Slapback
Slapback are very short delays, usually with just a single echo. These are often used in blues guitar tones and can also be applied too vocals. John Lennon is a great example.
Doubling
Vocal doubling are useful delay effects that isn’t really perceived as a delay. It uses a single echo that is incredibly subtle to create a chorus type effect. You can compare vocal doubling to a double-track vocal recording – very useful.
Long Delays
Typically longer delays are synchronised to the overall BPM of your project. These longer delays can have multiple echos that repeat to create interesting rhythmical patterns. Great for adding depth and atmosphere to an audio track.
Ping-pong Delays
Ping-pong delays are basically 2 synchronised delays in a single delay unit. The first delay is panned to the left and the second delay to the right channel of a stereo track. You can set different delay times for each of the 2 delays which can create some interesting rhythms that are only linked by the projects tempo.