MXD is file format in which the maps created from ArcGIS software can be stored. MXD not only stores maps but also stores the symbology, layout, hyperlinks, toolbars added, etc. at the time of saving the map document. An MXD can be distributed along with the data; hence whenever the MXD is opened the symbology, layout, order of layer always remains same. Custom buttons or tools added to the MXD are also retained.
