L3 cache is a type of memory used in computers to improve processing speed. It acts as a buffer between the CPU and the main memory (RAM), storing frequently accessed data and instructions. This helps reduce the time the CPU takes to retrieve information, enhancing overall performance. Unlike L1 and L2 caches, which are smaller and faster, L3 cache is larger but slightly slower. It is shared among multiple cores in a multi-core processor, allowing them to access the same data quickly. This shared access helps improve efficiency and reduces latency in data processing tasks.