Database connections allow database servers and software to interact with each other in an efficient manner. Of course, this statement still holds true in Martini's environment.
Using registered database connections, services will be able communicate with your databases and perform operations against them. You're also free to remove and update existing connections, as well as enable or disable them.
More about SQL services...
To view the existing database connections of your instance, open the Navigator view. Navigate to your instance's node, and under this node, expand the Databases node.
To perform an action on a database connection, right click its entry and select from the list of actions in the context menu that will appear. Depending on the state of your connection, some actions may or may not be executable.