Hey Jimmy,
For effects like reverb, flange, chorus, and so forth most mixers have mono sends and stero returns. This is because the track source is mono but the effect will then pan across the entire mix. Also realize that your effect is a mix of the "dry" source and the "wet" effect. What this does is allow your "dry" source to be panned into the stereo field where you want it but allow the effect to move across the stereo field to give depth perception--much like live music does in classical music with each intstument being a mono source but the music does move across the room though a violin on the left side of stage will sound as if it is from the left side of stage. That being said, certain effects, like EQ and compression for a total mix are not added "wet", they are there to give definite shape to a mix and particularly so in a final mix or master. These work either by sending your main outs directly to such devices in stereo and then the stereo outs of this device to your recording device. Some more expensive mixers will have main "inserts" so you can actually hear the result to be recorded. In a lot of cases you must here the mix as it comes from these devices. You can also send a track to such a device through channel inserts, but this is usually done before it has been recorded on portastudios (such as the FD-4 or FD-8, though it may be, I'm not sure since I don't have mine yet). Short and sweet, I guess I would have to say, don't be too concern about it, it works, really. I hope all that helped clarify your question. By the way, that is the recording engineer in you trying to figure this out. Congrats for taking the next step.
Peace, Jim
