Heat transfer is when the finished product comes out, you paste it on something else, and the ink is transferred to something else.
Silk screen printing is through the screen version (there are many holes on the screen version, like the screen window, but the holes are very small) to put ink on it, which is a metaphor for the general gift cup and cultural shirt. Then scraping, so that a part of the ink flows down through the hole, the substrate is below, and the ink from silk screen is very thick.
The cost of digital printing is very high, generally only for printing a small amount of things, such as bidding documents. The accuracy of digital printing is not low, but the cost is too high. You can think of it as digital proofing.
The range of four-color printing is a little wide. General printing can be four-color printing, but we usually say flat offset printing. It is through ink balance to transfer ink from PS version to blanket and then to substrate. Generally, the books and periodicals we read are printed in this way.