It's or its?

• It's is only used instead of it is or it has.
• Its is used to show the possessive form of it. This can be confusing because the possessive form of a noun does indeed have an apostrophe, for example the chair's leg is correct but it's leg is incorrect; it should be its leg.
• Its' - there is no such word in the English language.

Correct use of it's

• It's Wednesday today. (This is correct as it is a shortened form of it is Wednesday today.)
• It's exceeded my expectations. (This is correct as it is a shortened form of it has exceeded my expectations.)

Correct use of its

• I like your horse; what is its name?
• What a lovely dog - look at its cute face!

It's and its combined

• It's a table and it's got four legs. Its legs are made of oak.