Pronouns are used instead of repeating the same word many times. They commonly refer backward to a name or idea, but they can also refer forward. It is important to understand which idea the pronouns refers to in order to fully understand the text. These are some of the most commonly used pronouns:

People
he, she, we, you, they, my, your, her, his, our, their, me, him, her, his, our. 

Objects and ideas
it, this, these, those, that, there, its.