MDAC 2.5 SDK - OLE DB Programmer's Reference
Chapter 1: Overview of OLE DB
Binding structures describe relationships between elements in a consumer structure and columns in a rowset or parameters in a text command. Consumers use binding structures to communicate to providers how they expect data to be transferred from the provider to the consumer's buffer, and vice versa. Binding structures include information such as the column or parameter being accessed, the data type in the consumer's buffer, the offset to the data in the consumer's data structure, the amount of space available for the data value, and the precision and scale for numeric values. For columns containing COM objects, the consumer can also request the interface that must be returned to the consumer when the object is fetched.
Accessors are groups of binding structures that enable consumers to define simultaneous access to multiple columns or parameters and enable providers to optimize access to these multiple columns or parameters.