Petri nets are a mathematical modeling tool used to represent and analyze systems that involve concurrent processes. They consist of places, transitions, and tokens, where places represent conditions or states, transitions represent events that can change these states, and tokens indicate the current state of the system. These models are particularly useful in fields like computer science, systems engineering, and operations research for visualizing workflows and understanding system behavior. By using Petri nets, researchers can identify potential bottlenecks, optimize processes, and ensure that systems function efficiently under various conditions.