Contractions are used a lot in English, especially in spoken English.  You use contractions in written English if you want to convey a conversational or casual style, but you do not use them in a formal essay or presentation. As a rule. But you can go very wrong if you misuse contractions.  Here are a few tips on usage. The word contract means to squeeze together, and that is what contractions do – they join two words to make one.

commonly used contractions

I’m: I am
Can’t: can not
We’ve: we have
She’ll: she will
He’s: he is
They’d: they would
Won’t: will not
Weren’t: were not
Wasn’t: was not
Wouldn’t: would not
Shouldn’t: should not
Isn’t: is not

It’s and Its
It’s and its are the most confused words in the English language!  It is when shortened to create it’s is often confused with the possessive pronoun (homophone): its.

It’s is a contraction for it is or it has. For example:
I know it’s not that exciting.
It’s  a boy!

Its is a possessive pronoun. Its modifies a noun and is used to show ownership. For example:
The lion stalked its prey

To decide whether to use it’s or its, replace the word with it is or it has. If this makes sense as a sentence, you must use it’s. If not, use its.
“The bakery makes it is croissant twice a day” makes no sense. You must in this case use its.
“It is time to leave” makes sense. You can use it’s

They’re, Their and There
They’re, their and there are very commonly confused words for English language learners and we deal with the distinction in a different post.

You will find that you use contractions constantly in spoken English, so it is good to know how to use them and the difference between a contraction and a possessive pronoun.