The way the molds push through the plastic - Thermoforming

I think its like some heated plastic and they put something under it before sucking the air out and making it form around whatever is under it.

Here is a video that explains it. I think its almost the same as the gif.
https://www.youtube.com/watch?v=145qytKw6PU

Nah. I did watched videos of it and there is nothing under it. Just holes and they press air though this holes under the heated plastic. But i don't understand how they get it that good with just a few holes.. :s it's like magic

That video is not thermoforming. It is vacuum molding. In vacuum molding a “blank” is used and then the vacuum molded material is formed to the surface through negative pressure. Many quality functional composite pieces like car or aircraft parts are made through vacuum molding composites like carbon fiber, Kevlar, or blends. Thermoforming uses molds in the shape of the product. There are many types of molding, each has strengths and weaknesses. Thermoforming allows fast and cheap creation of parts as well as recycling of unused excess “trimmings,” but materials and design are somewhat limited by the equipment available. Here is a video explaining thermoforming: https://m.youtube.com/watch?v=alq3RDZN4jo