The most common effect used by guitarists is reverb (reverberation) which is like a continuous echo effect. When you make any sound in a room, that sound reflects back off the walls, floor, roof and any objects in the room. Reverb effects imitate these natural reflections.
Like distortion, the amount of reverb can be controlled and shaped by the controls on the pedal or unit. Many amps have reverb units built into them and you control the amount of reverb with a single dial or "pot". Play the following example using different amounts of reverb.