lets see. I will try to list out on the various looping thing short and sweet. For more indepth info. Google is the answer
1) Effect loop on amp- This one, many say that put your modulation effect(delay, phaser, flanger blah blah blah etc) in the effect loop of your amp for best result. I say if you have effect loop on your amp, go for it. Try it out and hear for yourself what different it will make and from there, decide accordingly whether you want your modulation effect to be in the effect loop or straight to amp input. Sequence of connection will be
Effect send--->pedals input and from the pedals output, go back to effect return on the amp.
2) True bypass looper- This one is a by product of the post internet forum pedal. What it does, is to isolate pedals which might not be true bypass and the player still want it to be in the chain of effect he/she wanna use.
Usually there will be a set of input and output jack on this pedal, plus another set of loop send and loop return jack.
3) Feedback looper- This one, is for making noise. The exterior of the pedal is like the true bypass looper except that the wiring in it is different by a bit. Put any of your modulation pedal within the loop, whatever your guitar signal go in from input and to output, the output signal will be fed back into the input, making it go hay wire, sound building on sound till the verge of amp speaker blowing. Best to have time based effect in the feedback looper for maximum chaos.
4) Looping device- This one is like a super long delay, it can record whatever your are playing, playback thru the amp and allowing you to overdub it. Eg of this are boss rc20xl/rc50, boomerang, gibson echoplex,
as for your questions, hehe, its pretty vague as in what sort of looping you are refering too. If you wanna know more, just google on, effect loop, true bypass looper, feedback looper or simply looping device