Floating slab
A slab poured separately from the surrounding foundation walls or footings, isolated so it can move independently without cracking or being cracked.
What does floating slab mean?
Isolating the slab from walls, columns, and footings prevents restraint, which is a major source of cracking as the slab shrinks and as the soil beneath it moves. The isolation is achieved with a compressible joint material at the perimeter and around penetrations. In frost-prone regions the term also describes a garage or shed slab that rides with seasonal ground movement instead of being anchored below frost.
In practice
The felt or foam strip you see between a garage slab and the foundation wall is what makes the slab float.