A cantilever is a rigid structural element, such as a beam or a plate, anchored at one end to a (usually vertical) support from which it protrudes; this connection could also be perpendicular to a flat, vertical surface such as a wall. Cantilevers can also be constructed with trusses or slabs. Cantilever construction allows overhanging structures without external bracing, in contrast to constructions supported at both ends with loads applied between the supports.
Sourced from Wikipedia.