A delay pedal records what you are playing and plays it back milliseconds later. This creates a cool echoing effect.
Some delay pedals have a clean, precise echo. These are often referred to as digital echo pedals. Others are designed to mimic the reel to reel tape machines of the past, including the distortion and noise of tape! If you can’t decide between digital or tape, some delay pedals like the Strymon Timeline include multiple styles of delay for you to choose from in the same pedal!
The loudness and the fade out of the repeating playback are the primary controls on a delay pedal.
A fast playback can create a “slapback” sound. Whereas a long gradual fade and repeat can create beautiful ambient echoes.