Brown United recently completed several structures for a California State Fair, including Truss Arching and Video Support.
Trusses are pre-fabricated, triangular structures used for support. They are extremely strong. The corners are connected with "nodes" and external forces result in compressive forces which enable the truss to support massive weight. A truss is composed of triangles because of the structural stability of that shape. A triangle is the simplest geometric figure that will not change shape (angles) when the lengths of the sides are fixed.
A planar truss is one where all the members and nodes lie within a two dimensional plane, while a space truss has members and nodes extending into three dimensions.