What is the difference between Widows 7 32 bit and Windows7 64 bit?

The 32 or 64 bit refer to the adressing capabilities of the OS. 32 bit can access only up to about 3.8 GB RAM where 64 bit can handle thousands of GB. In order to use the 64 bit Windows you also need a 32 bit processor installed in your computer. Most computers sold in the past 3 years have 64 bit processors