RSD Lite is the flashing program that Motorola uses the put software on the phones.
Fastboot are the install files that we can use if we mess up our phones to restore them to a normal state, while still maintaining our current apps and settings as FoxKat just demonstrated.
Matt's Utility v 1.8 has the files built into it so you don't have to use RSD lite you can just use option 1 on the utility and have your phone in AP fastboot mode.
OK I knew what RSD Lite was ... I used it to SBF my old Droid 2 back to Froyo because I didn't like Gingerbread. It's the fastboot that had me confuzzled. I have the last 3 of Matt's utilities saved just in case I need them, and they are awesome.
Thanks Sydman! :hail: