The left arrow will move the cursor one position to the left. If the cursor was at the beginning of a line, it will not move (the same as the up arrow when the cursor is already at the beginning of the file, and the down arrow when the cursor is already at the bottom of the file).
If number is typed immediately before pressing the arrow key, the position of the cursor will move number positions in the direction of the arrow. If number was too large, a beep will be heard, and nothing will happen.
For terminals with no functional arrow keys, four keys will move the cursor around: