64bit vs. 32 bit

[particlepat]

What's the difference between the two?

[jayd512]

This page should explain some of it:Should you choose 32-bit or 64-bit Linux?
See here as well.

One of the major differences is the amount of RAM that the 2 can handle.
32-bit will support up to 4 GB of RAM. 64-bit will support, in theory, up to 16 exabytes of RAM.

[Rubberman]

A couple of things to consider.

1. Even though a 32-bit system can address 4GB, some of that is used to map external device memory, such as video RAM, etc. As a result, only about 3.5GB is usable by the OS. A 64-bit OS doesn't have that problem since device memory can be mapped most anywhere it's convenient.
2. Recent performance comparisons of several Linux distributions' 32-bit and 64-bit versions have shown that for most benchmarks, 64-bit is starting to pull away from 32-bit.
3. Some current netboot/notebook processors, such as the Atom chip, are not 64-bit capable.

So, if you have more than 3 GB of RAM and a recent processor with 64-bit capabilities, then don't worry about going 64-bit all the way. All 64-bit linux distributions also run 32-bit software without any problems at all (at least that I've seen).

[oz]

What's the difference between the two?

Your question has a very broad scope they way it's worded, but note that a 64-bit capable processor can run 32-bit or 64-bit operating systems whereas a 32-bit processor can only run 32-bit operating systems. You can also check the 32-bit wikipedia page in addition to the 64-bit page as suggested above by jad512 for additional information.