How does the use of cache memory in modern computer systems improve the efficiency and speed of memory access, and what are the implications of having multiple levels of cache $($L$1,$ L$2,$ L$3)?$

Cache memory, being closer to the CPU, stores copies of frequently accessed data from the main memory, reducing the time the CPU spends waiting for data. Multiple cache levels $($L$1,$ L$2,$ L$3)$ provide a hierarchy of storage, with each level being slightly slower but larger than the previous one, allowing for a more efficient and tiered data retrieval process.