You use em in either snippets or chain them together and use them in a whole song. Or you just drop a lead solo in or a background riff or chunking to fill in the sound.

Sorta like these ones. I used Jason's techno loops (at PeaceLoveProductions) and added in my own guitar loops afterwards.
Then with audio applications like Cubase you can transpose and time stretch them.

http://s93744050.onlinehome.us/60secLoopDemo_Schmange.wav
http://s93744050.onlinehome.us/RockSplosion.mp3
http://s93744050.onlinehome.us/mp3/CovertOperation.mp3


It probably took a few months in my spare time to make the loops. Ya just sit down at the computer and improvise to a drum beat while you're watching TV or whatever. The recording is the easy part...
Then you have to sit there and splice them up into 4, 8 and 16 bar parts.
I'm up to about 10,000 loops already but only have about 4,000 edited so far. I'm kinda warn out from doing loops right now so I'm gonna rest a couple of months then go back at it.
PeaceLoveProductions is going to cover mine exclusively for now, starting with the release of 120BPM loops in E covering Rock, Wah, Acoustic, Guitar Synth etc. Then every couple of months he's adding different keys and tempos. Then I'm starting my own site called AxeLoops.com later this year and offering my own with techno/rock backup loops to complement them.

Figure it this way. Most guys with home studios tend to write stuff that's very synth oriented. This way you can drop in an acoustic, rock or even synth guitar in the background or use the ideas to write a new song.
You just drop in 8 bars and copy and paste through as much of the song as you want. It's sorta like using GarageBand except you don't get the cheezy sounding "Band-in-a-Box" generic guitar loops that everybody else uses.