Working with the Home folder for your map
One of the key workspaces in ArcMap is each map document's home folder, which is the folder location where your map document is stored. The Home folder is used by default in ArcMap to save results, store new datasets, and access file-based information. It is the location that is initially used to add new layers to ArcMap and to store new datasets that are created during editing and geoprocessing.
The same is true for nonspatial data. When you export a page layout as PDF, the default location will be the map's "home" location (the map document's workspace folder). The map's default geodatabase can be accessed using the Catalog window; it is highlighted and has the default geodatabase icon.
Setting and changing the map's Home folder
Any time you copy a map document to a new file folder location, that will become the maps' home folder. You can use this to organize ArcGIS information. For example, a common folder might be used to hold a number of related map documents, in which case they share a common home folder.
You can access the map's home folder in the Catalog window by clicking the Home button.