Megaflops???

What are megaflops, i know they have to do with processors and that’s what MAC’s use. But what do they have in relationship to PC’s. I looked up the name and it told me about millions of Floating operations per second FLOPS but what does this really matter to me. And should i find out which processor has the best megaflops and get that for my new computer.I have read that AMD has better MegaFlop ratings then INTEL, is this right and should i invest in a new AMD or stick with my INTEL chips. I also read that Supercomputers use GigaFlops and i guess thats pretty damn good. Ne help on this topic would be greatly appreciated.