A CPU cache is a small, high-speed storage area located inside or very close to the central processing unit (CPU) of a computer. It temporarily holds frequently accessed data and instructions, allowing the CPU to retrieve them more quickly than if it had to access the main memory (RAM). This speeds up processing and improves overall system performance. There are typically multiple levels of cache, labeled as L1, L2, and sometimes L3. The L1 cache is the smallest and fastest, while the L2 cache is larger but slightly slower. The L3 cache is even larger and shared among multiple CPU cores, further enhancing efficiency.