What makes floating hardwood floors different from traditional hardwood flooring is that such floors aren't glued or nailed to the wood subfloor or concrete slab. The planks are attached to each other, and sit on top of the subfloor or sound barrier.
The floor is installed with a small expansion gap at all edges, to allow for some natural expansion and contraction due to the seasons. The expansion gaps are never seen, they are covered by molding or shoe trim, and door thresholds (see diagram at right). (Source: BC Hardwood)