32bit vs 64bit memory with 32bits, you can go up to around 4 000 000 000, which, in terms of memory, would be 4GB. This means with a 32bits system, you can only address up to 4GB of memory, which is why many systems have a limit of 4GB RAM. With 64 bits, the limit would be... 16x10^18 or something. The system basically works with chunks of 64bits instead of 32bits, which mean data can be passed on faster. The OS itself has 2 different versions, because pretty much all functions can be re-made more efficiently with 64bits. This is probably not exactly right, but that's the main idea I guess. Wikipedia could probably answer you better.