Common English contractions and their meanings:

Isn’t = is not

Won’t = will not
Should’ve = should have
Would’ve = would have
It’s = it is (some people use this as the possessive form of “it”, but that is incorrect)
Haven’t = have not
Couldn’t = could not
Ain’t = are not/am not (this is informal and used widely in the southern US)
Shouldn’t = should not
Wouldn’t = would not
Could’ve = could have
Can’t = cannot
Hasn’t = has not
(If I forgot any common ones, feel free to put them in the comments)
If you have any questions about these, feel free to ask them in the comments or DM me