CMOS in an acronym for Complementary Metal Oxide Semiconductor (usually Silicon). You can look at the Wikipedia article for more detail but the most important aspect of CMOS for this article is that if it is in the off state or in the on state it uses essentially zero energy and therefore produces much less heat than other logic families. All our processors, RAM, etc. are made with this technology.
CMOS consumes energy and produces heat in the process of switching from the off to the on state and vice-versa. And the faster it switches, the more heat it produces. If you have been following the CPU clock speed progression, you will have noticed that it has plateaued for the past half decade at around 3.2GHz. This is solely because of the difficulty of wicking away the heat from the processor. In production machines cost issues still lead to aluminum or in some cases copper heat sinks attached firmly with springs to the top of the processor with a thin layer of heat conductive paste between them. A fan or fans are affixed to the apparatus to keep the heat sink itself cool. If you open the case of a desktop type computer and look at the heat sink, you will notice that it is heavily finned to increase surface area and thus enhances the ability to dissipate heat. Other more efficient technologies are available, but are only used by gamers who overclock (run the CPU at a clock speed higher than advertised by the manufacturer). These usually are liquid cooled with a pump and radiator. All our old IBM mainframes back in the day used water cooling. A really far-out cooler could use a mini-air-conditioner or even cryogenics.
So you say, “Joe how do we get our computers going faster? The Microsoft operating system is killing us with bloat.” For that answer stay tuned.