What is the difference between 32 bit and 64 bit

Hear alot about 64 bit applications, don't have any myself since I don't understand the difference between 32 and 64. Does it take a different type of PC (or operating system)to run 64 bit programs? If not, why would you install the 64 - for speed? I don't see many 64 bit applications offered. Since I just purchased a high end gaming machine, and the subject never came up ( they only asked about what type of applications I wanted to run in determining a custom, read expensive, config), I'm worried that I did not get a high end machine that would last me several years and be able to run any type of software.

Thanks for any info on this subject.

 

http://en.wikipedia.org/wiki/64-bit

http://zone.ni.com/devzone/cda/tut/p/id/5709

http://www.infopackets.com/news/har...it_vs_64_bit_systems_whats_the_difference.htm

 

Thanks for the reference material. I got about 50% of what I read. Lasting impression was that Microsoft is not that gung ho about long term support for x64. The bottom line for me is if my computer is upgradable beyond the 4gb I currently have installed (and which is not totally used), what's the point of having the ability to add more memory in a 32x system?