An indefinite pronoun does not refer to any specific person, thing or amount. It is vague and "not definite". Some typical indefinite pronouns are:
all, another, any, anybody/anyone, anything, each, everybody/everyone, everything, few, many, nobody, none, one, several, some, somebody/someone
Most indefinite pronouns are either singular or plural. However, some of them can be singular in one context and plural in another. The most common indefinite pronouns are listed below, with examples, as singular, plural or singular/plural.
Notice that a singular pronoun takes a singular verb AND that any personal pronoun should also agree (in number and gender). Look at these examples:
Each of the players has a doctor.
I met two girls. One has given me her phone number.
Similarly, plural pronouns need plural agreement:
Many have expressed their views.