Feathering your prop means turning the blades so that the edge of the blades is into the oncoming wind. Single engined aircraft do not have this feater as it is only used on props attached to dead engines and a single engined aircraft with a dead engine has a pilot who needs to bail out, not fiddle with the prop.
What it does is stop the propellor from windmilling, e.g. being turned by the air flowing over it, and greatly reduces drag. A windmilling prop can "runaway" and violently detache from the aircraft or start a fire in the dead engine. The drag produces an unstable aircraft that is being pulled forward by the working engine on one side and held back on the otherside by the dead engine and windmilling prop. Feathering the prop solves both these problems.
