The vector (0,2) points directly north and the length of this vector is 2 units. It's the distance from (0,0) to (0,2).
When rotating 270 degrees counterclockwise, we'll turn to the left or westward direction (90 degrees so far) then at some point aim directly south (180 degrees so far) and finally ultimately end up pointing directly east (after getting to 270). So that's how we go from (0,2) to (2,0).
If you were to go clockwise, then everything flips and you'll ultimately end up pointing directly west. The length of the vector stays the same the whole time.
