This idea is ideal for those of you you play through an amp and monitor speakers while on stage.
Sometimes it may be good to use the monitor speakers as part of your amp: You have an extra speaker around. This extra speaker may be useful for particular special effects while using your pedals. One of those effects is the idea of “stereo-delay” 

The image of “Stereo Delay” only comes alive when using two amps. Using two amps on stage may not always be practical. What about using the P. A monitor speaker as part of your amp?By using the insert input of the mixer you are able to send your Delay signal through that particular channel of the mixer: Simply patch the delay pedal into the insert input.

Insert inputs work as patching an effect onto one channel. You will need a cable with a stereo- Jack plug on one side going into two mono-Jack plugs. The stereo Jack plug is usually plugged into the mixer, while the two mono-Jack plugs are for your delay pedal: One Jack plug for the input while the other Jack plug goes into the output of your Delay pedal. The stereo- Jack sends the unprocessed signal of the channel into your Delay while the output of the Delay brings the signal back into the channel. A bit like an effects-loop, with the difference that the insert will only work for one dedicated channel.

The delayed guitar signal will only be heard on the monitor speaker, while your guitar amp in unprocessed. Make sure you do not plug the Delay straight into your guitaramp, since this will put delay onto both guitar amp and monitor speaker.

Using the insert input in this manner creates the idea of Stereo-image: Guitar amp is dry while monitor speakers do have the delayed signal. The monitor speaker will probably not be that close to your guitar amp, this makes the stereo idea work even better.

Inserts inputs do not only work  for Delays, they will take any effect. Try it to see which effects work best for you while using the insert input of your mixer. 

Happy experimenting,
Eddie