A beam is a structural element that is capable of withstanding load primarily by resisting bending. The bending force induced into the material of the beam as a result of the external loads, own weight, span and external reactions to these loads is called a bending moment.
Beams are traditionally descriptions of building or civil engineering structural elements, but smaller structures such as truck or automobile frames, machine frames, and other mechanical or structural systems contain beam structures that are designed and analyzed in a similar fashion.
In engineering, beams are of several types:

• Simply supported – a beam supported on the ends which are free to rotate and have no moment resistance.

• Fixed – a beam supported on both ends and restrained from rotation.

• Over hanging – a simple beam extending beyond its support on one end.

• Double overhanging – a simple beam with both ends extending beyond its supports on both ends..

• Continuous – a beam extending over more than two supports.

• Cantilever – a projecting beam fixed only at one end.

• Trussed – a beam strengthened by adding a cable or rod to form a truss.