Singular pronouns are simply pronouns that refer to singular nouns. But it can get a little tricky when you think about the fact that singular pronouns can be personal pronouns, which, as you have learned, refer to a person or thing. They will also be definite or indefinite, which means they can refer to someone or something specific (definite) or not (indefinite).
So words like he and she are singular, personal, definite pronouns, and words like anybody and anyone are singular, indefinite pronouns.
Plural pronouns are simply pronouns that refer to plural nouns. But, like singular pronouns, plural pronouns can also be personal and definite or indefinite, and they refer to plural nouns or groups of nouns.
For example, words like they and we are plural, personal, definite pronouns, and words like many and both are plural, indefinite pronouns.