On an artificial wall, holds are usually man-made pieces (sometimes real rock) that are attached to the wall by bolts that go through them and into the wall. Holds are all different shapes and sizes. The configuration of holds on the wall determines the "route," or the path to the top that the climber must follow.
Different kinds of holds have different names. Some are specific descriptions related to the shape of the hold, such as a chickenhead (a round hold that sticks out from the wall) or a bone or a urinal (deep, scooping hold). But there are also broad universal descriptions for how a hold works and how it is used:
Some "moves" that climbers use to get from hold to hold also have names.
Bucket: A big hold, or one that is in-cut, that you can really get your hand into or around.
Crimper: A crimper is a small hold, just big enough for the fingertips, that you have to crimp your fingers to hold on to. A climb with lots of crimpers is "crimpy."
Downpull: A hold that can be used by pulling straight down. Usually very solid and straightforward.
Finger pocket: A one- or two-finger pocket is a hold with a depression that you can only get that many fingers into.
Gaston: A move where one or both hands pull on a hold across the front of the body. Imagine it as trying to open closed elevator doors with one or both hands.
Pinch: A hold that you squeeze the outsides of in order to hold on to it.
Sloper: Any hold that slopes downward so that you can"t lock onto it. Slopers are easy to slide or "grease" off of.
Sidepull: A hold that"s turned so it can only be used from the side. This kind of hold usually takes trickier body position.