Quantum chemistry is one of the most powerful and widely used methods for studying interactions in chemical systems today. Quantum chemical calculations can straightforwardly generate electron wavefunctions. According to the principles of quantum mechanics, the electron wavefunction contains all the information of the system. Wavefunction analysis is a general term for a large class of methods that transform the complex electron wavefunction into information with clear chemical and physical meanings. Compared with common theoretical approaches for studying interactions, such as structure optimization and energy calculations, wavefunction analysis provides key complementary insights into the characteristics of interactions.