Combat damage is the damage that's dealt automatically by attacking and blocking creatures. Any other damage is noncombat damage, even if it's dealt during a combat phase by an attacking or blocking creature.

Fear of Burning Alive's last ability deals damage equal to the amount of noncombat damage dealt by the source that dealt damage to an opponent.

If a source you control deals noncombat damage to multiple opponents simultaneously while there are four or more card types among cards in your graveyard, Fear of Burning Alive's last ability will trigger once for each opponent dealt noncombat damage this way.