Pronouns in English are distinguished based on the gender of the person to which the pronoun refers:

Bill sprained his ankle.

-- "His" is the male pronoun

Mary lost her book.

-- "Her" is the female pronoun

English does not have a singular gender -independent personal pronoun. Traditionally, the singular pronoun "he" has been used to refer to both sexes, but this is now regarded as sexist:

Anyone who wants lunch must present his ticket at the counter.

This problem can be removed in two ways.
The first method is to use "he or she" or "he/she" in place of "he":

Anyone who wants lunch must present his or her ticket at the counter.

The second method is to use a plural indefinite pronoun in place of the singular:

All people who want lunch must present their tickets at the counter.

The third method is to rewrite the sentence to eliminate indefinite pronouns entirely:

If you want lunch, present your ticket at the counter.

Note that the following sentence is incorrect, because the plural pronoun "their" is inconsistent with the singular indefinite pronoun "everyone":

Everyone who wants lunch must present their tickets at the counter.

When using pronouns to stand for compound subjects whose individual parts are of mixed gender, use at least one pronoun of each gender:

Either Jim or Helen will bring his car or her car.
Either Jim will bring his car or Helen will bring hers.