src: secure.img1-fg.wfcdn.com
A floating shelf is a form of shelf with its wall fixings hidden within the shelf board, with no visible supporting brackets. A floating shelf may have two or more channels open from the back towards, but without reaching, the front, into which slide fasteners attached to the wall, typically held in place by screws inserted through the bottom of the shelf.
For typical floating shelf supports, a supplier suggests that floating brackets with a diameter of 12mm can support a shelf at least 22mm thick loaded with 20kg, and 18mm brackets can support 30kg on a 28mm shelf.
Video Floating shelf
References
Source of the article : Wikipedia