In BG3, Dash is a bonus action.
The D&D 5e rules set, make that you can use your action or bonus action in the order you may choose and your movement scattered between those actions and bonus action as you see fit.
Exemple, you can move 9 meters in a turn, you may move 3 meters to reach a creature, use your action to do an attack, you kill that creature, then you move toward another creature with your remaining 6 meters but that's not enough, then you use your bonus action to dash to reach the next creature, you use your action surge feature to get a second action on this turn and use that said second action to do an attack.
A turn, whoever you are or whatever you are, is
- Move
- Action
- Bonus action
- Reaction
Consider those as ''slots'' which you can use place and trigger specific features from your race, class, etc., some classes gives features that will consume your bonus action like the spell Shield Of Faith, or the rage feature of a barbarian. Some races or classes don't gives features that use your bonus action. You decide what order you want to use your bonus action, action, reaction, movement (which you divide the way you desire between all your actions/bonus actions).
For a barbarian, isn't rare to start with the bonus action to trigger his rage feature and then moving toward the enemy and use the action to do an attack with the bonus implied by the rage feature.
