Circuit theory is a branch of electrical engineering that focuses on the behavior of electrical circuits. It involves analyzing how voltage, current, and resistance interact within a circuit. Key components include resistors, capacitors, and inductors, which help determine how electrical energy is distributed and used. In circuit theory, various laws and principles, such as Ohm's Law and Kirchhoff's Laws, are used to calculate and predict circuit performance. These laws help engineers design efficient circuits for applications ranging from simple electronic devices to complex systems like computers and telecommunications.