A possessive adjective is used before a noun.

A possessive pronoun is not used before a noun.

I am a teacher.

This is my website.

This website is mine.

You are a student.

Is that your chair?

Is that chair yours?

This is a woman.

Her hair is red.

My hair is brown. Hers is red.

This is a crocodile.

It's showing its teeth.

("Its" is used for animals and things.)

We are working on our websites.

The websites are ours.

(mine + yours = ours)

You are students.

You are in your classroom. This classroom is yours.

They are children.

They are eating their popsicles. The popsicles are theirs.