What exactly do people mean when they say “wildfires started by arson?”

Obviously there are the climate change denialists who think “global elites” have paid actors setting forest fires around the globe, but there are also reputable people saying this. When I hear arson, I hear a person starting a fire with malicious intent. Are there really massive numbers of malicious firestarters around the globe, or does arson also cover things like recklessness/carelessness, like if I burn trash in my backyard or start a campfire on the woods and it gets out of control?