The new Auto Discovery feature in Enterprise Manager Cloud Control 12c uses IP Scan (NMAP) to discover host and non-host Targets without the need for an Agent, scanning your network and discovering all the hosts thereon. Certain information about which software is running on the hosts comes from smart guesses. This goes into a list of discovered unmanaged Targets in Enterprise Manager.
The DBA can then select any Target host from this list and promote it as a managed Target; this then pushes the Enterprise Manager Agent to the server. The Agent then performs deep discovery of all Targets on the server and collects the detailed configuration.
Setup | Add Target | Configure Auto Discovery brings up the screen shown in the following ...