"Both" means two (2). You can use "both" to describe two things, two people, two ideas, etc. Its use often helps to emphasize certain qualities or conditions. It can be a pronoun, an adjective, or a conjunction.
1. Both of these students attend the same school.
2. These girls love Christmas. Both of them are expecting to get a lot of presents this year.
(Notice that "of them" comes after "both. You can also say "Both are expecting a lot of presents this year.")
3. Sunflowers are both beautiful and edible.
(In this example, two adjectives come after the word "both.")
4. Both men are fierce competitors.
5. Many women have to choose between raising a family or advancing in a career. Some try to do both.