AMRAP stands for as many reps as possible. Instead of a set number of reps, each work interval is a target to beat: do as many good-form reps as you can until the timer says stop, rest, then go again.
In Intervals One, that's how every move works unless you give it a rep target. It suits almost any interval workout, from a gentle 30/30 bodyweight session to a hard 45/15 circuit, and it makes progress easy to see: count your reps in each interval and try to beat them next time.
You'll also see AMRAP used for as many rounds as possible: one long block, often 10 to 20 minutes, where you work through a short list of moves again and again until time runs out. That works in the app too, as a single long work interval. Want a fixed number of reps instead, with the rest of the interval to recover? That's an EMOM.