Complex sentence: It provides a layer between programming languages and OLE DB (a means of accessing data stores, whether they be databases or otherwise, in a uniform manner), which allows a developer to write programs which access data, without knowing how the database is implemented.
Split into simpler sentences: It provides a layer between programming languages and OLE DB (a means of accessing data stores, whether they be databases or otherwise, in a uniform manner). ADO allows a developer to write programs that access data without knowing how the database is implemented.