Floating: In a floating floor installation your laminate floor is not fastened to the subfloor. Foam moisture barrier (underlay) is first laid over the subfloor. The new flooring is then laid over the moisture barrier. There are many different underlay product available. The most common is Polyethylene Foam Underlay with Moisture Barrier.
Polyethelene Foam instalation instructions
Quiet Walk is highly reputable brand (something I would be comfortable using in my home).
Quiet Walk instalation instructions