We all have a learning curve, so asking questions is normal.
The bearings are ment to ride on the perimiter of your material and alow the profile cutter to follow the shape, conversly the bushings are to follow a template and guide the cutters without bearings.
There are also other uses for the cutters with bearings one primarily comes to mind is triming laminate counter tops where there is a slight overhang, the cutter follows the edge of the workpiece and makes a small bevel to smooth the top surface where it meets the vertical.
For the bushings imagine you wanted to make slots in something, there would be a guide that would be larger than the slot and using the busing follow the slot with a small diameter cutter to produce the correct shape, also used for cutting dovetails, the bushings fit in a router base designed for them and keep the machine from digging past the desired depth.
Last edited by Kristin D; 12-05-2011 at 08:07 PM.