Beeswax foundation is a sheet (which can be reinforced with plastic) of beeswax. It is placed in the middle of a frame in such a way as to employ bee space. This forces the bees to build a comb in the area we wish them to. Foundationless beekeeping refers to the method of beekeeping where we use beehive frames without foundation.
There are two broad categories of frames in use. Plastic ones and wooden ones. Plastic frames often have a plastic center foundation that has honeycomb patterns on it and is coated with beeswax to give the bees a hint that they can draw comb on it.