In Esperanto we do not use "ĝi" to refer to concepts, at all (unlike in English, where we often use 'it'). We use "tio" to refer to concepts in Esperanto. Think of it this way - "ĝi" is a pronoun, meaning that it takes the place of a noun. Don't use "ĝi" unless you can actually name the noun it is replacing:
La hundo estas bruna (The dog is brown)
=> Ĝi estas bruna (It is brown) ("ĝi" refers to "la hundo")

"Tio" can be used to refer back to phrases and concepts, much as "ĝi" refers to nouns.

We saw a glimmering of this a while back, in the forum postings about Miland breaking down the door of a pub.

Esperanto uses this distinction to avoid ambiguity that sometimes pops up in other languages. I'll give an example not involving Miland.

My dog likes to lick my face. It is good.

We have two possible meanings here; one, that my dog is good (and he likes to lick my face). Two, that it is a good thing that my dog likes to lick my face.

This sentence is not ambiguous in Esperanto.

Mia hundo ŝatas leki mian vizaĝon.

"Ĝi estas bona" - this means that my dog is good. I am commenting only on my dog, not on the action of my dog licking my face. Technically I could be saying that my face is good but due to context, this isn't likely.

"Tio estas bona" - this means that it's a good thing that my dog is licking my face. "Tio" is replacing the entire phrase "Mia hundo ŝatas leki mian vizaĝon". In my previous example, "ĝi" was only able to replace a single noun, which in this case was "mia hundo". Ĝi cannot replace phrases, it can only replace nouns. Tio can replace phrases.

The other common use of "tio" is to represent nebulous ideas. This was discussed elsewhere; it's like saying "I like that!" without really specifying what.

For the record, English uses "it" far, far, far more often than Esperanto uses "ĝi". In some cases, like what I mentioned above, Esperanto uses "tio" instead. In some cases, Esperanto uses nothing, such as with "impersonal" verbs. These are verbs with no subject.

In English, verbs must have a subject, even if it's just a meaningless placeholder. That's why we say "It is raining". What, exactly, is raining? The sky? In this case, "it" doesn't replace anything. We only use it in the sentence because English doesn't accept verbs with no subject; you can't just say "Is raining" or "Rains".

In Esperanto, you CAN say simply "Is raining". Weather words do not have a subject (because weather just happens, no one is specifically performing the action). So:
Pluvas = It's raining
Neĝas = It's snowing
etc.

We never use "ĝi" for these expressions, even though English uses "it".

Non-weather verbs can also be impersonal. If I want to say "It's good to see you", I don't need to make up a fake subject "it" in Esperanto. I say simply "Estas bone vidi vin" (no subject)

Actually, I have seen ĝi used to refer to concepts, in older Esperanto. I saw it in «Alicio en Mirlando» (though that may have been nonstandard usage), but I also thought I saw it mentioned in PMEG and/or another thread. Maybe someone else can find it… Personally, though, I dislike that usage.

As far as the idea that English sentences should not end in prepositions—“That is a rule up with which I shall not put.”* It’s the most utterly nonsensical, artificial and plain wrong “rule” I’ve ever heard. Never has it been standard usage. It’s worse than the idea that infinitives should never be split.

* Attr. to Winston Churchill

Rogir:No, it's not a choice, in certain situations you must not use it. That is in cases where 'it' does not refer to anything, and is used as a placeholder, for example

It was a bad idea to go there. - Estis malbona ideo iri tien.
It is raining. - Pluvas.
It was nice talking to you. Estis agrable paroli kun vi.

It is a white rabbit. - Ĝi estas blanka kuniklo.
It has been done. - Ĝi estas farita.

Well, I hope you get the idea.

Also, I guess if you took the sentence "It was a bad idea to go there", you can shuffle the word order around to "A bad idea was to go there", taking out 'it' entirely. I reckon if you can do that in English and retain the same meaning, then 'goodbye' to ĝi in Esperanto

And jchthys, if 'with' is a conjunction, then technically "That is a rule which I shall not put up with" ('up with' being the part moved to 'match' the apparent rule) doesn't end in a preposition . Not to discredit Winston Churchill's sense of humour lol

jchthys:As far as the idea that English sentences should not end in prepositions—“That is a rule up with which I shall not put.”* It’s the most utterly nonsensical, artificial and plain wrong “rule” I’ve ever heard. Never has it been standard usage.

Indeed, although the avoidance of stranded prepositions and the need for it is something long disputed among grammarians, so I see it as more of a stylistic thing than a rule about "correct" grammar. As you point out, there are many cases where you simply can't make "correct" usage of a preposition without sounding utterly absurd by normative standards. I guess English is just broken beyond all repair

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tommjames:

jchthys:As far as the idea that English sentences should not end in prepositions—“That is a rule up with which I shall not put.”* It’s the most utterly nonsensical, artificial and plain wrong “rule” I’ve ever heard. Never has it been standard usage.

Indeed, although the avoidance of stranded prepositions and the need for it is something long disputed among grammarians, so I see it as more of a stylistic thing than a rule about "correct" grammar. As you point out, there are many cases where you simply can't make "correct" usage of a preposition without sounding utterly absurd by normative standards. I guess English is just broken beyond all repair

You can blame good ol’ Bishop Lowth et al. for all those silly rules. I seem to recall the reasoning was: “the word preposition has ‘pre’ in it, so it must appear before something.” Or maybe that’s just apocryphal.

What they were after was “dignifying” English so that it could be a polite language on par with the rest of Europe. In reality, they were applying Latin rules of grammar to English. Latin infinitives can’t be split, right then, neither can English infinitives. In fact, prescribing language in terms of Latin was very common back in the day – I have even seen Cherokee grammar described in Latin terms... what a mess!

I occasionally drop pronouns in Esperanto, but only when it is obvious what the omitted pronoun would be.

For example I might say: "Mi ŝatas dormi dum aŭskultas la pluvon. Mi pensas ke estas kvietan."

I know this probably isn't correct, as I am far from an Esperanto expert. Just throwing in my du cendoj

Greyshades:I occasionally drop pronouns in Esperanto, but only when it is obvious what the omitted pronoun would be.

For example I might say: "Mi ŝatas dormi dum aŭskultas la pluvon. Mi pensas ke estas kvietan."

I know this probably isn't correct, as I am far from an Esperanto expert. Just throwing in my du cendoj

It isn't correct and I would recommend against doing that. As with any language, I think it's better to be conservative with your usage until you learn what is and isn't acceptable variation from the norm, as per the community. Just because Esperanto is owned by its community doesn't mean that people speak it any old way. If you omit pronouns, you will come off as someone who doesn't speak the language well enough to know any better. Elegance and brevity in speaking is valued by the community, but not at the expense of incorrect grammar.

(btw, no -n with "estas". So you'd say "Mi pensas ke estas trankvile" - I think that it's tranquil. kvieta means quiet in the sense of not noisy; trankvila means tranquil or peaceful. It's a -e ending, not -a, because you are describing a verb [estas] not a noun)

erinja:

It isn't correct and I would recommend against doing that. As with any language, I think it's better to be conservative with your usage until you learn what is and isn't acceptable variation from the norm, as per the community. Just because Esperanto is owned by its community doesn't mean that people speak it any old way. If you omit pronouns, you will come off as someone who doesn't speak the language well enough to know any better. Elegance and brevity in speaking is valued by the community, but not at the expense of incorrect grammar.

(btw, no -n with "estas". So you'd say "Mi pensas ke estas trankvile" - I think that it's tranquil. kvieta means quiet in the sense of not noisy; trankvila means tranquil or peaceful. It's a -e ending, not -a, because you are describing a verb [estas] not a noun)

Lol okay thanks for the advice, I'm not really part of the Esperanto community I just am very intruiged by the language and have spent several months studying...

I was a little lazy with the example, I'll admit, and I also tend to not care about the accusative (I think that's how you spell it) ending -n when talking to myself. I kinda laughed when I read a description of Ido cause it sounds a little more laid back and easier to speak out loud.

Okay, I'll be honest and say I'm very lazy

Well Ido is somewhat more similar to English as far as grammar is concerned, so it's good for us lazy English-speaking peoples . I wouldn't advise against learning both though, it's fun to see the differences between EO and Ido.