L3 Cache is a type of memory used in computers to store frequently accessed data and instructions. It acts as a buffer between the CPU and the main memory (RAM), helping to speed up data retrieval. By keeping important information closer to the processor, L3 Cache reduces the time it takes for the CPU to access data, improving overall system performance. Typically larger than L1 and L2 Cache, L3 Cache is shared among multiple cores in a multi-core processor. This shared design allows for efficient communication and data sharing between cores, enhancing the performance of multi-threaded applications and tasks.