Cantilever
A cantilever is a structural element that projects horizontally beyond its support and is held at one end only, with no column or wall beneath its free end.
Cantilevers appear constantly in contemporary homes: a first floor oversailing the ground floor, a balcony with no posts, an eave extending for shade, a bench or stair tread that appears to float. The visual appeal is that the structure looks effortless, because the means of support is hidden inside the building.
Structurally the load is carried back through the element into the supporting structure as bending and shear, which is resisted by a counterweight or a fixed connection. That is why a cantilevered slab typically extends back into the building at least as far as it projects out.
The practical limits are deflection and cost. The further a cantilever reaches, the deeper or stronger the member has to be, and the more the free end will move under load. Cantilevers are set out with an engineer from the outset; they are not something to add late in documentation.