Complex sentence: ODBC provides a universal middleware layer between the application and DBMS, allowing the application developers to only have to learn a single interface, nor do they have to update their software if changes are made to the DBMS specification, only the driver needs updating.
Split into simpler sentences: ODBC provides a universal middleware layer between the application and DBMS, allowing the application developer to use a single interface. If changes are made to the DBMS specification, only the driver needs updating.