When a
CPU is looking for the next bit of
code to execute, the first place it searches is the speedy
L1 cache. If the data it needs exists in the cache, this is referred to as a "cache hit". Otherwise, the CPU must search the
L2 cache, then
main memory, and finally, in the worst-case scenario, the data will need to be paged from the
hard drive.
This term could also be used to refer to a similar situation in any other caching system, such as a browser cache.