Here is a simple plot with some extra elements that we haven't seen before. There are smaller tic marks between the major, labeled tic marks. These are referred to as minor tics. There is also a grid of dotted lines covering the graph, with the grid lines aligned with the major tic marks.
The following script will create the previous figure:
set grid set mxtics 4 set mytics 2 plot [0:2*pi] sin(12*x)*exp(-x/4)
The new commands are in the highlighted lines.
set grid causes the light grid lines to appear when we finally issue the plot command. The second and third lines create minor tics on the axes.