Below from the B757/767 FCTM:
“Maximum Rate Climb
A maximum rate climb provides both high climb rates and minimum time to cruise altitude. Maximum rate climb can be approximated by using the following:
757-200, 757-300
• flaps up maneuver speed + 50 knots until intercepting 0.76M
767-200, 767-300, 767-400
• flaps up maneuver speed + 50 knots until intercepting 0.78M
Note: The FMC does not provide maximum rate climb speeds.
Maximum Angle Climb
The FMC provides maximum angle climb speeds. Maximum angle climb speed is normally used for obstacle clearance, minimum crossing altitude or to reach a specified altitude in a minimum distance. It varies with gross weight and provides approximately the same climb gradient as flaps up maneuver speed.”
So for a 90t jet, Max rate climb speed would be approx 280kts, max angle climb speed approx 230kts.
Max rate is used, for example, to climb to FL280 in the shortest time possible. Max angle to, for example, reach FL280 in the shortest forward distance, say by a specific waypoint.