Vortex ring state, or settling with power, is like punching the down elevator button for a helicopter. When a helicopter descends too fast in its own downwash, the rotor blades become less effective, and a rapid descent begins. If too close to the ground, a recovery could be impossible.
In normal flight the rotor blades’ tip vortices circle up and then back through the disc, reducing the rotor’s effectiveness. In VRS, as the ship settles into its own downwash, the tip vortices grow and the rotor becomes increasingly ineffective until air is coming up through the disc, seriously degrading lift.
For decades pilots have trained to recover from VRS by reducing power and flying forward or laterally out of the dirty column of air. Now a newer technique has been pioneered that promises to keep altitude loss to around 50 feet or less.