God's Algorithm
From Speedsolving.com Wiki
God's algorithm is the optimal solution from a puzzle state to another state, commonly the solved state. The term is sometimes used to refer to such an algorithm itself, or an algorithmic procedure that finds God's Algorithm efficiently.
God's Number
God's number is unknown for 3x3x3. The superflip is known to require 20 moves in HTM, and Rokicki has proven an upper bound of 22 moves for any position.