There are guides covering coming terms in the hacking and the RS sections here, stickied to make it easier to find.
eg:
http://www.droidforums.net/forum/droid-hacks/632-what-root-means-stop-asking.html (you dont have to stop asking, that's just the title of the thread
)
Think of a
rom as an image you can apply to a device. In the workplace images are often ghosted and applied to computers to save time in configuring a system. On our phones a rom is a snapshot of the operating system.
People root their phones through the act of
rooting. They gain admin rights to replace files they normally can't. Think of it as an admin user on w windows pc that has more access then regular users.
hacking is what we are doing when we seek out methods to alter our phone. We hack to figure things out. We are hacking when we discover as well as when we apply changes.
The droid 1 has a
bootloader that is not locked down. We can
root the phone and
hack it to then apply a
rom to it.
Currently the Droid-x and some other phones have a locked down bootloader. That bootloader requires the roms to be signed in order to install new ones. That means hacking developers can't make roms that can be installed on the droid-x at this time.
Flash the wrong rom to your phone and it can make it unusable. In trying to hack the phone it is possible you could swap out some files, in the attempt to make it do what you wanted, and screw it up.
Gaining root in itself will not brick your phone but once you obtain it you can alter any file on the phone. Remove or alter the wrong one....and you'll be asking Verizon to fix your phone for you if you can't replace the file. A system dump has been made that lets you get missing apps back if you tried to get rid of some "bloat ware" but if you wreck the os bad enough you'll need to get it reinstalled.