as a determiner (followed by a noun, but not by a pronoun): Both children are at school.
as a predeterminer (followed by a word such as ‘the’, ‘this’, ‘his’ etc): I like both these pictures.Both her children are boys.
as a pronoun: Both arrived at the same time. (followed by ‘of’): Both of them are learning English. (after a noun or pronoun subject): The twins both have black hair. (following a pronoun object): I like them both. (after a modal or auxiliary verb, or after the verb ‘to be’): We can both speak Spanish.They are both good singers.
in the expression both...and...: a method that is both simple and effective