Damage can be direct, damage over time, or AOE. Abilities can involve multiple types of damage.

You can identify DOTs by either the tooltip descriptions, or if in doubt look at the combat text - they show up differently (the damage is reported in small, orange numbers to the lower right of an enemy instead of over their head). AOEs affect multiple enemies and are placed on an area, not a specific target. Like Templar’s jabs. Everything else is direct damage.

An example of a multi damage type ability is bow’s poison inject or snipe. These land an initial hit of direct damage, then start DOT ticks. Or you mentioned lava whip (straight direct damage) so you’re probably a DK. Fire breath offers an initial hit of direct damage, then DOTs. So that ability could proc a monster helm that procs off direct or off of damage over time.

Light and heavy attacks are mostly direct damage too. Some aren’t...like a lightning staff heavy is channeled, so it isn’t. But all lights are direct, and most heavies.