“The creative impulses of man are always at war with the possessive impulses” – Van Wyck Brooks
A possessive noun is a noun that shows that something belongs to a person, place, thing, or idea.
To make a noun possessive add an apostrophe (’) and an s to the end. The kid’s toy.
Watch out for s and z sounds. Words that end with these sounds just get the apostrophe: The kids’ toys.
Some classical names and words that would be hard to pronounce may get just an apostrophe as well: Moses’ burning bush.
Words ending in y may change to ies’. The fly’s buzzing or the flies’ buzzing. Depending on if the noun is plural or not.
Possession across multiple nouns is indicated in the last noun listed. Bob, Jim and Frank’s boat.
When two nouns refer to the same person the second noun gets the possessive case. But this can read really badly and should probably be reworded in the way: The father of the girl’s necktie was red. It’s a confusing jumble though technically correct. The girl’s father wore a red necktie sounds better.
Inanimate objects are not supposed to possess anything. They should use the word “of” instead of being granted apostrophe+s treatment. The book of matches, not the book’s matches.
There are exceptions to this (the razor’s edge), but there are no real rules governing this so take such issues on a case-by-case basis.