MDAC 2.5 SDK - Technical Articles
A data link enables you to easily store connection information within an application or to pass it between applications. The format of a data link is a connection string, which is a string version of the initialization properties needed to connect to a data store. Without a connection string, it would be necessary to store or pass a complex array of structures to access data.
The Data Link API exposes a user interface that you can implement in your applications to create and manage connections to OLE DB data stores.