When you want to make a printed circuit on a small scale, there are several methods to do this. One involves specific chemicals, which are not so great. In these tutorials, vinegar and hydrogen peroxide is used, which should be more environmentally friendly.
With a laserprinter you print your circuit on glossy paper, using the Toner transfer method.
The etching itself is the process where the printed circuit stays and the copper is etched of.
Here you see the procedure explained in French, here in English.
These links are documented as a mnemonic.