I want an explanation (nothing - something - everything - something)

Indefinite pronouns are used to refer to nonspecific people, things or places. In this way, the speaker uses - body or - one to refer to people, and - thing to indicate objects. As a general rule, these pronouns are consider to be in the singular form so the verb has to agree with it.

It is important to highlight that "Nothing" is used in negative sentences (example: Nobody worked yesterday.)

"Something" is used for unknown or nonspecific object and it is appears in affirmative sentences. (Example: I saw something in the kitchen).

"Everything" is used to refer to a total amount of nonspecific objects and it appears in affirmative sentences. (Example: I bought everything yesterday).