Delay effect is widely used in electronic music and lot of other genres as well. It’s a great way to add dense or ethereal quality to synthlines, pads, vocals or whatever sounds. I use delay a lot in my own productions to add that extra atmosphere to otherwise dull sounds.
Here’s a quick introduction on how simple delay effect affects to the sound. The effect unit in this tutorial video is Fruity Delay 2, one of the easiest and handiest delay effect there is.