A truss is an assembly of members such as beams, connected by nodes, that creates a rigid structure.
Truss bridge for a single-track railway, converted to pedestrian use and pipeline support. In this example the truss is a group of triangular units supporting the bridge.
Historical detail of a steel truss with an actual revolute joint
Planar roof trusses
The roof trusses of the Basilica di Santa Croce in Florence
A beam is a structural element that primarily resists loads applied laterally across the beam's axis. Its mode of deflection is primarily by bending, as loads produce reaction forces at the beam's support points and internal bending moments, shear, stresses, strains, and deflections. Beams are characterized by their manner of support, profile, equilibrium conditions, length, and material.
A beam of PSL lumber installed to replace a load-bearing wall
An I shaped beam of metal under a bridge