What effect does cache memory have

I do not know a lot about processors but I would like to know about cache memory? What is actually that L1Â cache, L2 cache and others, does the cache memory have any effect on the processing speed of a computer and why is the size of cache memory so low? I have also noticed that the core i3, i5 and i7 have a larger volume of cache memory. Are the cache memory a part of processors?Â
