64 bit is generally a little faster, so if you have a 64bit CPU it would be best to use 64 bit Linux.
The underlying differences between 32 bit and 64 bit are really beyond the scope of this guide however, there are a few standard “rules of thumb” to help you choose which one is right for your system: Regarding the functionality of the desktop, both images are virtually identical. We presently offer two different images: one for 32 bit systems (i386), and one for 64 bit systems (amd64). iso files, which are commonly referred to as “disk images”. Naturally the first thing you’ll need to do in order to get up and running is to download the image.