There are two types of SDE databases: Stand-alone and Client/Server.

Stand-alone versions are installed on a single host computer. Only the user of the host computer has access to a stand-alone SDE database.

On a Client/Server or network installation, multiple users can access the same SDE database once they map the network drive from their computer to the network location where the database is stored. The advantage of a network location for the database is that all users have access to the same copy of the database.