A CyclicBarrier is a synchronization aid in Java that allows a set of threads to wait for each other to reach a common barrier point before proceeding. It is particularly useful in scenarios where multiple threads need to perform a task in phases, ensuring that all threads complete their current phase before moving on to the next one. When a thread reaches the barrier, it calls the await() method. If the specified number of threads has reached the barrier, they are all released to continue execution. If not, the thread will wait until the required number of threads arrive, making it a powerful tool for coordinating parallel tasks.