Critical Resolved Shear Stress (CRSS) is single crystal equivalent of yield stress of normal strain strain curve. It tells about the minimum shear stress required for slip in a single crystal.
In single crystal, by variation in orientation of sample the amount of force required to start slip changes because of the change in CRSS at different orientation.
To know this value, a formula is derived which you can refer in Page 124 of Dieter book. However we have tried to explain through video. Kindly watch this video and subscribe to our channel.