Practical examples of settling with power:
1) Aircraft is able to Hover in ground effect (just) at SL. It departs and then attempts to land at 8000 feet, maximum power is applied but it is insufficient to arrest the rate of decent.
2) The aircraft at gross weight attempts to land with a 15 knot tail wind. Maximum power is applied but insufficient to arrest rate of decent.
3) If you have ever come into a landing spot and had to over torque to get stopped at the bottom, that is settling with power.