Active mode is the default mode for opening a draft document for viewing and editing. All commands are available. Drawing views, parts lists, drawing tables, and other items are checked to determine whether they are out-of-date. Model geometry is live and accessible.
The counterpart to this is review mode.
You can set a draft document to active mode using the Activate Drawing Views for Editing option on the Open File dialog box or by choosing Applications→Activate Drawing Views when the document is already open.