Some nouns function as possessive nouns.
Possessive nouns show ownership.
You typically form the possessive of a word by adding an apostrophe + s to the end of the word.
If the word is plural and ends in an "s", then you just add the apostrophe after the s. If the plural doesn't end in "s", add the apostrophe + s.
When a name ends in "s", it is typically acceptable to use the apostrophe + s or just add the apostrophe.
Examples of possessive nouns:
Dogs' (more than one dog)
Children's (plural not ending in s)
Chris's or Chris' (name ending in s)
Examples of possessive nouns in a sentence:
1) Mark's dog is a Labrador retriever.
2) My sister's phone is lost.
3) Are we going to the Smith's house?
4) The girl's bookbags were left on the gym floor during class.
5) I was sorry to find out that Tom's cat died.
6) The bus driver's hat was crooked.
7) I am not sure that the men's restroom is on this hallway.
8) My mom's name is Leslie.
9) The football team's jerseys are red.
10) The flowers' petals are starting to open.