Adding on to the above answer, you can say "Keep smiling" as a goodbye greeting to a close friend. You want that person to be happy and smile a lot. Keep Moving is also used to ask someone (in an encouraging way) to not be deterred and to continuously move ahead in life without getting discouraged by anything.

Keep out = Do not enter. If you see a sign that says "keep out" you are expected to stop and not enter. Keep smile = This phrase does not make sense. Keep smiling = Smile continuously because it will make you feel better. Keep move = This phrase does not make sense Keep moving = Do not stop.