It's a term from full size 4x4 ing..
A full floater axle means the the wheel/hub is supported by it's own bearings, and the axle will slide completely out, with the hub still connected to the vehicle. The axle "floats" and isn't supported by bearings at the the wheel side, so you can unbolt it, and slide it right out.
There are many advantages of a full floater, one being less stress on the axle, but a GREAT advantage is being able to pull the axles without messing with brakes, wheels, hubs, etc. just a series of bolts around the outside.. you can pull the axles and still tow the vehicle.. with a locked rear end, you can break an axle, and still get out of the woods.. just pull the broken axle (or the outer piece of it in many cases)
Also, for pulling third members, it is great, cause you just pull each axles a few inches, unbolt the pumpkin, and pull her out!
Disc brakes on top of it, make it a real winner.. I will be watching this with great interest