FrameTicks is an option for two-dimensional graphics functions that specifies tick marks for the edges of a frame.
The following settings can be given for FrameTicks:
When tick mark specifications are given separately for each edge, the edges are ordered clockwise starting from the bottom of the frame.
With the Automatic setting, tick marks are usually placed at points whose coordinates have the minimum number of digits in their decimal representation.
For each edge, tick marks can be specified as described in the notes for Ticks.
See The Mathematica Book: Section 1.9.3 and Section 2.9.5.
See also: Ticks, GridLines, FaceGrids.