an EDMS is an Electronic Document Management System.
It's not part of AutoCAD, it's a separate software system in it's own right. However, the system I use is closely integrated with AutoCAD.
For example, I have all the attributes in my title blocks linked to the system along with a number of other attributes and blocks that I use on a regular basis. The EDMS automatically extracts the values from these attributes and stores them in the database. I can then search on these attributes and other values to find any drawings, or other documents. I also use it to control MS Office documents as I can extract data from these as well.
The EDMS automatically keeps a revision of any document that is changed and I can go back to them and compare documents to see what has changed and when.
Production also use it to view and plot drawings, thus ensuring they always have the latest revision level.