Anything with a bunch of levels or stages can be considered a gradation. In high school, the process of moving from freshman to senior year could be called a gradation, or your position in the series of steps that lead toward graduation.
Any organization with a hierarchy, set up so that some members are considered better, higher, or more respected than others, has a gradation of positions within it. The military is a great example, with a gradation, or series of steps, from private to general. The root of gradation is the Latin gradationem, which means "ascent by steps."
