how does somebody "burn the coffee"?

Leave the hot plate on more than 3 hours. Or microwave reheat it too long. It's fairly delicate and will scorch at too high temperature.

If you leave coffee in a pot that's sitting on a hot plate (like the heated plate on many coffee makers), the water starts to evaporate out. This super heats the remaining solids in the coffee, and it lets out bitter oils and resins that taste burned. If you leave it set long enough, all the water boils out and you're left with a kind of coffee tar that you'll never get out of the pot.

But, if you use a drip coffee machine or coffee press, you can't burn the coffee in the brewing process. Hot water will only get up to 212F. If it got any hotter, it would be steam. And, about 200-205F is the ideal temperature for brewing coffee to extract a maximum of flavor and a minimum of bitterness. However, if you use one of those old percolators, where the water bubbles up and gets repeatedly dispersed over the coffee grounds in the basket, this will overheat the coffee that's percolating and result in burned, bitter flavor.

some people burn there coffee with a torch because they prefer the taste of burnt coffee.

By adding boiling water straight to beans.

Either a bit of cold water or milk should be added first.

u cant