In studio (and live) usage, sends are used a lot for bussing effects. For example, if you had a reverb unit, a physical unit I mean, you would have a good plate verb for vocal for example, and you can send all the vocals to that channel (and adjust the reverb unit to only pass through 100% wet, no original sound at all), they then have the same sounding reverb on them with just 1 unit.
You can adjust any channels send levels from the mixer. When you select channel 1, the turn dials under the send channels dictate how much of ch 1 goes to each send. When you select channel 2, the dials change to represent how much of ch 2 is going to each send.
A good example of using sends is having a 100% wet delay on the send channel. This way you can process the delay more without affecting the original signal: Add Fruity Delay 2 to the send channel of your choice, and turn the "dry" knob all the way down. This way you wont double the undelayed sound. Adjust time and feedback to taste. Then add a Fruity Free Filter below the delay, set it's mix level on 50% and set it on a high-resonance HP filter. Then automate the filter frequency and you got much more life in your delay chain.
Another example is splitting bass by frequency. You can use fruity's routing for this too but sends work fine also: Take a gritty bass sound to channel 1. first fx slot, use the Fruity Send, route the signal to send ch 1. On your bass channel's 2nd fx slot, use a EQ and lowpass from 200Hz. On send 1's first FX slot, use EQ and highpass from 200Hz or higher. Now you can add distortion, filtering, chorus, autowah, delay or whatever on the high end of your bass sound without mushing up the low end. Reverbing bass this way can work nicely if the high end is stabby.
