Indefinite pronouns refer to people or things in a general manner, or people or things whose identity isn't important.
Sounds cruel to us. Who are these pronouns to say who or what is or isn't important? Stupid elitist pronouns.
Indefinite pronouns don't have an antecedent, or something they refer to; they just stand on their lonesome.
Here are some of the most popular, in demand indefinite pronouns: