A pronoun allows flexibility in writing because it is a word that stands for a noun. Without pronouns, writing and speech would sound unnatural and boring. Compare the following two sentences.
Charlie left Charlie's house, taking Charlie's dog with Charlie.
Charlie left his house, taking his dog with him.
The second sentence is much better.
Dividing pronouns into groups based on what they do shows how many purposes they serve.
Personal pronouns ( I, me, he, she, it, etc.) stand for one or more persons or things, and differ in form depending on their case; that is, how they are used in a phrase, clause, or sentence. For example, when acting as a subject, the first-person singular pronoun is I. When acting as an object, the correct pronoun is me.
Reflexive (intensive) pronouns
Reflexive or intensive pronouns combine some of the personal pronouns with -self or -selves ( myself, himself, themselves, etc.). Reflexive pronouns are used to reflect nouns or pronouns, as in He hurt himself; or to emphasize, as in I myself don't believe it. Although people often use reflexive pronouns as subjects and objects in speech, don't do this in your writing.
Tom and I don't like it.
NOT Tom and myself don't like it.
Rob doesn't like Luke or me.
NOT Rob doesn't like Luke or myself.
Demonstrative pronouns ( this, that, these, those) point out what you are talking about.
These are the most economical, but this is the one we want.
When they stand alone in place of nouns, these words are pronouns. But when they precede nouns, they are adjectives: this car, that word, these shoes.
Relative pronouns ( who, whom, which, that) introduce clauses that describe nouns or pronouns.
The professor who wrote the textbook is teaching the class.
The storm that caused the power outage has moved east.
The trend is toward using that and which interchangeably, although many teachers and editors prefer to maintain a distinction. Use that when the clause that follows it is restrictive: when it provides information necessary to define your subject. Use which when the clause that follows it is nonrestrictive: when it adds information that isn't necessary to define your subject.
The car that hit her was green.
NOT The car which hit her was green.
The relative clause that hit her restricts or limits the subject, car. The information in the clause is necessary to the main statement.
The car, which I bought a week ago, gets good mileage.
NOT The car, that I bought a week ago, gets good mileage.
The clause which I bought a week ago adds information about the subject that isn't necessary to our understanding of the main statement that the car gets good mileage.
Use commas around a which clause but not with a that clause.
Interrogative pronouns ( who, whom, whose, which, what) introduce questions.
Which is the best one to choose?
What is your destination?
Who asked the question?
Indefinite pronouns don't specify the persons or things they refer to. The most frequently used indefinite pronouns are all, any, anybody, anyone, both, each, either, everybody, everyone, few, many, neither, nobody, none, no one, one, several, some, somebody, and someone. Like other pronouns, indefinite pronouns stand in for nouns, even if those nouns aren't specified.
Many are called but few are chosen.
Nobody likes a tattletale.