Sometimes we use a pronoun instead of a noun, if the meaning is clear.
The English pronouns include words like 'I', 'you', 'them', 'us', 'mine', 'his', 'this', 'those', 'one', 'ones', 'someone', 'anything', 'everywhere' and 'nobody'.
Here's a list of all the explanations and exercises about pronouns.
Subject and object pronouns explanation
Subject and object pronouns exercise
Possessive pronouns and possessive determiners (adjectives) explanation
Possessive pronouns and possessive determiners (adjectives) exercise
Indefinite pronouns explanation (something, anyone, nowhere, everybody, etc.)
Indefinite pronouns exercise (something, anyone, nowhere, everybody, etc.)
Possessive pronouns explanation
Possessive pronouns exercise
Relative pronouns explanation
Relative pronouns exercise
Reflexive pronouns explanation
Reflexive pronouns exercise