Steerable Downhole Drilling Mud Motors
A steerable downhole drilling mud motors system allows directional changes (azimuth and/or inclination) of the well without tripping pipe to change the Bottom hole Assembly BHA, hence its name. This article is one of the Directional Drilling guide articles I recommend visiting to understand other deflection tool mechanisms.
https://www.drillingmanual.com/steerable-downhole-drilling-mud-motor-systems/