Difference between desired yaw and yaw

I would want to know the difference between the desired yaw and yaw as shown in the log snippet attached. From replaying the flight in the online log viewer, the vehicle tends to be the flying backwards on the outbound leg and nearly sideways.

Or it could be yawing about North. What would the graph look like if it went from 359deg to 1deg and back again?

Hi Dave, can you come a bit clearer??