Well first I'm going to be talking about the possessive case, the genitive case, where apostrophes show possession or a relationship between two things.
首先讲解一下所有格，省字符表示的是两种事物之间的所属关系。
英语百科
Genitive case
In grammar, genitive (abbreviated gen; also called the possessive case or second case) is the grammatical case that marks a noun as modifying another noun. It often marks a noun as being the possessor of another noun; however, it can also indicate various other relationships than possession: certain verbs may take arguments in the genitive case, and it may have adverbial uses (see Adverbial genitive).