“Loopers” have been one of the more popular guitar effects in recent years. Loopers are not an “effect” so much as a device which can record a segment of music as you play it and then play it in a loop until you decide to stop it. You can select your “in” and “out” points as you play with a foot switch and some loopers will allow you to add multiple layers to your loop.
In this case, a video is worth a thousand words, so here is Sergio Altamura of (surprise, surprise) CandyRat Records using a looper in his tune “Before the Sea”:
Loopers can be used in a number of ways. Obviously, as seen in this video, they can be used as a composition and performance tool. They are also a great practice tool. You can record a chord progression or a riff and then play along with it, or you can record a segment of a tune that you are working on and listen objectively to see how it sounds.
If you think a looper is something that you could have some fun with (I know I do – though I don’t actually own one yet), then take your guitar to your local guitar shop and try one (or more) out.