A reciprocal pronoun is a pronoun which is used to indicate that two or more people are carrying out or have carried out an action of some type, with both receiving the benefits or consequences of that action simultaneously. Any time something is done or given in return, reciprocal pronouns are used. The same is true any time mutual action is expressed.
There are only two reciprocal pronouns. Both of them allow you to make sentences simpler. They are especially useful when you need to express the same general idea more than once.
Reciprocal pronouns are easy to use. When you want to refer to two people, you will normally use "each other." When referring to more than two people, for example the students in a lecture hall, you will normally use "one another."
Reciprocal pronouns help prevent repetition within sentences. In the following examples, reciprocal pronouns have been italicized for ease of identification.