Honestly, they probably aren't that useful. Most questions that include the phrase "bonus action" aren't asking about the bonus action themselves, and likely have it from a rules text quote like this:
> **Cunning Action**
> Starting at 2nd Level, your quick thinking and agility allow you to move and act quickly. You can take a **Bonus Action** on each of your turns in Combat. This action can be used only to take the Dash, Disengage, or Hide action.