How are pronouns and contractions different?

Pronouns are Words that take the place of nouns in a sentence; for example:

When George got to 19th Street, he got off the train. (The pronoun 'he' takes the place of the noun 'George' in the second part of the sentence.)

A contraction is a shortened form of a combination of Words indicated by an apostrophe in place of the letters that are missing; for example:

is'nt = is not

wasn't = was not

can't = can not

he'll = he will

we've = we have

you're = you are