Spool

[bluridr]

What is a spool or a mini spool?

[94cnytoy]

a spool or "mini-spool" essentially makes a 100% full time solid connection from your ring gear to your axles.
the axles(wheels)will not turn or move independantly.
unless or until an axle breaks.
a limited slip is a "clutch" type differential that has a pre-set "controlled" amount of traction aid.it will let the wheels turn at different speeds. it is very manageable on the street,snow and ice.mostly used for front end applications(allows for steering)
Locker: from detroits to ausi-loc to lockrights--all are "locked" when under power from the driveshaft.they will not let the wheels turn independantly under power. when off power(rolling thru a turn, they will let one wheel(with solid surface contact or "traction" turn faster than the other wheel. This setup is feasible for some on the road but has a definite driver learing curve(i'd not recommended for dd's or in the snow/ice belt for road driving on light trucks (5000# OR LESS)
electric locker/arb's/ox locker: these are the best of both worlds. They allow for "standard" open diff operation (1-wheel drive) and then can be "fully locked" like a spool when required. If you got the $$$ and your truck is driven on the road, these are the best thing going.
good luck.
ps: scroll through this post section, there lot's of locker input here. also, please give us some info on your vehicle and your plans hopes and dreams for it, I'm sure someone out there has done what you want, to the same vehicle and setup and will be able to give you specific vehicle/set-up advice from their own experience.