Pronouns are used to avoid repeating the same nouns over and over again. For example, "Jeremy ran so fast, you'd think his life was on the line." The pronoun "his" saved us from repeating the name Jeremy again. Common pronouns include I, me, mine, she, he, it, we, and us.
Pronouns are classified as personal (I, we, you, he, she, it, they), demonstrative (this, these, that, those), relative (who, which, that, as), indefinite (each, all, everyone, either, one, both, any, such, somebody), interrogative (who, which, what), reflexive (myself, herself), possessive (mine, yours, his, hers, ...
Nouns are words that refer to specific things or people: for example, phones, umbrellas, or Nicki Minaj. Pronouns, on the other hand, stand in for a previous noun: the same word can refer to several different things. They include words like those, them, and he.