- An apostrophe is a piece of punctuation use for the omission of letters which usually enable two words to merge together (in other words to show that letters have been removed or are missing. e.g - Do not can be contracted into one word: Don't)
- They also show possession between two things, such as Janet's car, Paul's hat, James's house (if a name ends with 's' it is optional to add the additional 's', but you can normally tell if it is needed by saying the word aloud to see if you pronounce the extra 's')
- Possession is also shown when you writ things like: My boss owes me two weeks' pay, or, I got two months' free M.O.T with my spaceship (not that many people would own a spaceship, but we can all dream...).
There are obviously many more examples and uses for apostrophes, these were just a few.
I hope this proved of some use to people. :)
P.s - Please note that plurals have no apostrophe, e.g. -
trees,
apples,
books ect. This is the same with possessive determiners & pronouns like
his,
hers,
theirs ect.