Automata theory is a branch of computer science that studies abstract machines, known as automata, and the problems they can solve. It provides a framework for understanding how machines process information and make decisions based on input. Automata can be classified into different types, such as finite automata, pushdown automata, and Turing machines, each with varying levels of complexity and computational power. The theory is fundamental to the design of programming languages, compilers, and algorithms. It helps in analyzing the capabilities and limitations of computational systems, providing insights into what can be computed and how efficiently. Automata theory also intersects with other fields, including formal language theory and complexity theory.