If you deliberately light logs on fire to roast marshmallows, you have camping skills. If you deliberately set your whole house on fire to collect the insurance money, you've committed arson.
The noun arson comes from the Latin word ardere, meaning "to burn." Arson is the act of setting something on fire for a nefarious purpose, and it is, of course, illegal. If you live in a wildfire risk area, you know that sometimes wildfires are caused by natural causes like lightening, sometimes they're caused accidentally by carelessness, and sadly they're sometimes caused by a deliberate act of arson.