Lifshitz theory, developed by Ilya Lifshitz, is a framework in statistical physics that describes phase transitions in systems with long-range interactions. It focuses on how fluctuations in a system can lead to changes in its state, particularly in the context of critical phenomena. The theory provides insights into the behavior of materials as they undergo transitions between different phases, such as from liquid to gas. The theory is particularly relevant in understanding critical points and universality classes, which categorize phase transitions based on their characteristics. Lifshitz theory has applications in various fields, including condensed matter physics and cosmology, where it helps explain the behavior of complex systems under varying conditions.