To show the grammatical function of a part of a sentence, function markers are used:

nominative

Some sentence functions, such as the subject, are recognizable for the fact that they don't have a function marker. Absence of this marker is called the nominative.

accusative

The sentence function of an object, along with several other functions, is recognizable by the N ending. This ending is called the accusative ending or simply the accusative.

prepositions

Many sentence functions of different types can be recognized by various short words called prepositions.