Bob, No pix, but visualize a sprocket on a shaft with the key ways lined up precisely with no key present. Then rotate the sprocket 2 degrees- and, viola, you have the profile of a 2 degree offset key. Obviously, the key becomes weaker as the offset grows, until the keyways pass each other. Say the key is 1/8 inch on a 1" shaft, 1 degree is -- you do the geometry- ? .oooo? inches.
I guess offset key are one way to sync two sprockets. Could adjust the belt or chain length or idler position. When they're all in sync-crank, cam, distrib, oil pump, FI pump, fan, diff, Mars, Venus, etc.-- That 250 will run smooth as silk- balance a Jefferson nickel on the valve cover.