In the "olden days" the only option for a bee hive frame was to have a beeswax foundation upon which the bees build out their comb. In order to give some strength to the foundation, there are wires embedded in the wax (the wax comes with vertical wires, and beekeepers themselves have to add the horizontal wires). Here's a picture of wax foundation with the embedded vertical wires:
While this is what is the most similar to the bee's natural environment, it is very labor intensive to put together a frame. It involves a 12V transformer to embed the horizontal wires in the wax. See an example of the steps you have to follow here and here (you have to do both sets of steps).
As a labor (and therefore cost) savings measure, people have come up with a plastic sheet, embossed with the necessary honeycomb pattern, that they then coat with a layer of wax. This sheet is stiff enough that you don't need any wires - you just snap it in the slots of the frame. They've even gone one farther - made a one piece frame/foundation combination out of plastic, and coated it with wax. One benefit of the plastic foundation is that it can come in black, which makes it easy to see the white eggs. Another benefit is when you spin frames, you have less to worry about the frame coming apart ("blowing out") due to the stresses of the extraction (since the foundation is plastic and not fragile wax).
Here's where the controversy comes in. There are beekeepers that swear up and down that the bees don't take to the plastic foundation as well as the wax. Others say they have no problems.
When I bought my hives, they came with wooden frames and plastic foundation., My experiences have been not so positive. I feel that last year I had a problem where the bees stripped off the wax from the plastic frame and used it elsewhere. After the wax is gone, the bees won't build on the bare plastic. Here's a picture of one of my frames from last year - I have a few like this, and others are completely bare:
The bees wouldn't build any more comb than you see here.
To try to salvage these frames, last week I bought a brick of beeswax. I melted some (and boy did the kitchen smell yummy!) and used a foam paint brush to brush on some more wax onto the plastic foundation. Here are the results:
I also bought some new frames with wired wax foundation. It'll take some work to assemble them, but I want to try them out in the hive to do some scientific comparisons as to how well the bees draw out the comb.
It's important to note that after the bees have drawn out the comb, there isn't any difference between the plastic and wax foundation. The bees work both just the same.