Compare-and-swap is an atomic operation used in computer science to manage concurrent processes. It works by comparing the current value of a variable with a given value. If they match, the variable is updated to a new value. This ensures that changes are made safely without interference from other processes. This technique is essential in multithreading environments, where multiple threads may attempt to modify shared data simultaneously. By using compare-and-swap, systems can avoid race conditions, ensuring data integrity and consistency while allowing efficient parallel execution.