To fill in a grid of lines between major tick marks use the GRID command. You must use BOX before GRID to compute the tick spacing. BOX does not label any axis. There are two string buffers maintained for the X and Y labels. Otherwise, it will use the string argument.
AXIS is a lower level command that draws an arbitrary axis.
It does not take into account the current viewport and world coordinates. Arguments to AXIS specify the position of the axis, it's range of data values, the format of the labels and spacing of ticks.