Milling is the process of removing one layer, or all the layers (called full-depth removal) of existing asphalt. This process grinds and pulverizes the existing asphalt into its original aggregate form.
Milling is done to remove deteriorated asphalt either to apply a new surface course, new full-depth asphalt, or for those pesky pothole repairs that everyone deals with.
Milling can also be used to repair low and sunken areas in existing asphalt to provide positive drainage before a surface overlay is applied.
Edge milling is similar and consists of milling edges of existing asphalt adjacent to a gutter pan, curb, or any structure for a smooth transition. This process can be facilitated if the existing asphalt has not deteriorated with much severity, thus saving substantial cost for sizable projects.
(Indianapolis Apartment Complex)