Frame is an option for two-dimensional graphics functions which specifies whether a frame should be drawn around the plot.
True by default draws a frame with tick marks. If Ticks
Automatic, setting Frame
True suppresses tick marks on axes.
See the Mathematica book: Section 1.9.3, Section 2.9.1, Section 2.9.5, Section 2.9.5.
See also: Boxed.
Here is one plot without and another with a frame drawn around it.
Evaluate the cells to compare the graphics.