Regular languages are a class of formal languages that can be defined using regular expressions or recognized by finite automata. They consist of strings made up of symbols from a finite alphabet and can be described by simple patterns. Regular languages are closed under operations like union, intersection, and complementation, making them versatile for various applications in computer science. These languages are important in the field of theoretical computer science and are used in compilers, text processing, and network protocols. Regular languages can be efficiently processed, allowing for quick pattern matching and searching tasks. Their simplicity makes them foundational in understanding more complex language classes.