Sure, the word pronoun is used often, but in the end it’s a little more complicated than just being a word used to replace a noun. At its base, that’s what it is, but there are various types, and some of those are mentioned briefly in this article.
Let’s get a point out of the way first: I’m not a professional in this field (or any for that matter), so please don’t take the information on this page in that manner. If for some reason you need language assistance of that type, don’t use this as a replacement for talking with someone who is qualified.
A possessive pronoun is one type that is commonly used. It replaces both a noun (or noun phrase, which is another topic) and a possessive adjective. Let’s say you’re at Phil’s house and talking with him about the surrounding landscape. You ask him, “How old is that tree?” Since there is actually a group of trees in the area, he doesn’t know which one you’re referring to, and asks for clarification: “Which one?” You respond, simply, by stating: “Yours.” In this case, the word “yours” replaces what would have been “your tree.”
Other types of pronouns exist, one of them being the personal pronoun. These replace people or objects. For instance, when you starting a sentence off with yourself, if your name happened to be Ben you wouldn’t say, “Ben likes peanut butter.” That would be talking in the third-person! Instead, you use the pronoun “I” and tell the person to whom you’re speaking, “I like peanut butter. It tastes great even by itself!”

