I think it has to do with if the Caliper is fixed, and has pistons on both sides of the rotor, or if the caliper has pistons only on one side, and "floats" on pins back and forth.....
Course, I could be totally wrong. The nomenclature can vary by manufacturer, poster, sobrity, your results may vary, past performance may not indicate future results, with approved credit, plus Tax, Title, and License fees.......
On full-floating, the rotor can slide side to side to center itself when clamped by the caliper, providing optimal contact of the pads against the rotor.
On non-floating, if the caliper and rotor aren't perfectly aligned, there can be uneven pressure on the inner and outer pads and less-than-optimal contact, so you don't get maximum possible braking force.
If you look at conventional rotors that are usually 1 piece. Steel in most cases. Floating refers to the mounting hardware. If you look at a floating rotor you will usually find that there are a series of small "rings" on the bottom or inside of the disc. Those little rings are held in place with springs and can move ever so slightly. Solid disc hold lots of heat when pressed in hard duty. Floating disc have a way to move within the mounting hardware and can distribute heat more evenly allowing for less fade. That's all I have. Hope most of it was accurate enough for the wrenches out there. I know there is lots more on this but it's as direct as I can make it.
The brake caliper is the assembly which houses the brake pads and pistons. The pistons are usually made of aluminum or chrome-plated iron. There are two types of calipers: floating or fixed. A fixed caliper does not move relative to the disc. It uses one or more pairs of pistons to clamp from each side of the disc, and is more complex and expensive than a floating caliper. A floating caliper (also called a "sliding caliper") moves with respect to the disc; a piston on one side of the disc pushes the inner brake pad until it makes contact with the braking surface, then pulls the caliper body with the outer brake pad so pressure is applied to both sides of the disc.
Floating caliper (single piston) designs are subject to failure due to sticking which can occur due to dirt or corrosion if the vehicle is not operated regularly. This can cause the pad attached to the caliper to rub on
Any fool knows that the difference between semi and full floating calipers refers to the specific density/gravity of the components involved. Basically one floats and the other has a neutral buoyancy. Since we know that unsprung weight is a MAJOR BAD, obviously, the lighter, "floating", version is better.
PS The proceeding is BS intended for the amusement of those that know. If you don't understand the difference erase what I just said from your memory, trust me, your understanding will be hurt by paying any attention to some of what what I just said.