Formal languages are structured systems of symbols and rules used to create strings that convey meaning. They are essential in computer science for defining programming languages, protocols, and data formats. By establishing a clear syntax and semantics, formal languages enable precise communication between humans and machines. In formal languages, each string is generated from a set of symbols and follows specific grammatical rules. This allows for the classification of languages into types, such as regular languages, context-free languages, and context-sensitive languages. Understanding these categories helps in the design of compilers and interpreters, which are crucial for software development.