Functional suspension training works by anchoring straps or rings so the user can train against body angle, gravity, and instability. The user's body provides most of the resistance, while strap length, foot position, handle height, and anchor point change the difficulty.
The appeal is adjustability. A row, press, squat assist, lunge, plank, fallout, or anti-rotation drill can become easier or harder with small setup changes. The tradeoff is that safe anchoring, body control, and clear progression matter more than the straps themselves.