Quelqu'un frappe à la porte.
English: Someone is knocking at the door.
Indefinite pronouns in French are words used to refer to people or things in a non-specific way, such as 'someone', 'something', or 'everyone'. They help you talk about things or people without naming them exactly.
Use indefinite pronouns in French when you want to talk about people or things in general, without specifying exactly who or what. They are useful when you don't know, don't want to say, or don't need to mention the exact identity.
Quelqu'un frappe à la porte.
English: Someone is knocking at the door.
Je n'ai rien compris.
English: I understood nothing.
Chacun doit apporter son livre.
English: Everyone must bring their book.
Personne n'est venu hier.
English: No one came yesterday.
Tout est possible.
English: Everything is possible.