What distro are you using? Normally there is a file in /etc which tells you what version of that distro you are using (for Debian it's /etc/debian_version; for RedHat /etc/redhat_release). Also with
you can find out information about the kernel you're using.
part refers to Intel based computers, either 32bit (x86) or 64bit (x86-64).
The other two refer to PowerPC CPU based computers; also 32 and 64bit version.