Cases

It is a grammatical category which reflects the function of a given element within a sentence. Nouns, adjectives and pronouns can have cases. English, Italian, French or Spanish don’t have cases, while languages like German, Russian, Latin, Polish, Finnish Hungarians do.

The case system poses a certain amount of difficulties to speakers of languages which have no case system, but they can be learned efficiently with the right approach

For more information look at Wikipedia:

https://en.wikipedia.org/wiki/Grammatical_case