The Graduated Filters allow you to make photo adjustments to specific portions of your photos.  You can apply a radial gradient - do add stylistic vignettes - or linear gradients - affecting just the top and bottom on the image.

For each of these styles of gradients, there are two sets of corrections you can define: inside and outside for radial gradients, and top and bottom for linear gradients.  These two sets of adjustments are shown at the bottom of the Graduated Filter tool.  The arrow button between these two sets swaps the settings on these two sets.

The adjustments you can make are the same as in the Finishing Tools.