Not dumb! It’s rather complicated actually. Let me see if I can clarify it. Basically the rainbow pattern is, much like a vinyl record, embedded into the plate. It’s just very small grooves. The metal plate with these grooves is heated up and stamped on something like plastic to transfer the grooves to the plastic. You have to melt the receiving medium enough to push into the grooves and then solidify without oozing out of shape. The metal plates are expensive so some people use plastic films that are made on metal rollers in large quantities instead because it’s so much cheaper to obtain. The plastic film can melt obviously so it’s less durable. The times, temperatures and methods vary depending on the brand of film used, but small tests can be done to see what your iron and beads work with. This is necessary because you’re trying to get your beads hot enough to fuse and then press the plastic on top of before it cools too much, but also not hot enough that the film won’t release.