What is a prism?
A prism is the solid shape you get if you move a flat polygon through space. A prism has five planes: a top, a bottom, and three sides. The most common kind of prism is a rectangular prism, made by moving a quadrilateral through space: a cube is a common example of a rectangular prism. The next most common kind of prism is a triangular prism, made by moving a triangle through space.
To figure out the surface area of a prism, calculate the surface area of each side and add them together. On a rectangular prism, each rectangular side is congruent (the same size) with the another one parallel to it.
To figure out the volume of a triangular prism, think of the prism as a rectanglar solid sliced in half. So you multiply the length by the height by the thickness, and then divide the result in half.
One useful thing that is in the shape of a triangular prism is a camping tent. Why might you need to know the volume of a tent? The attic of a house might also be in the shape of a triangular prism.