There are several key concepts that you need to be aware of when working with DBTNG. Many of these concepts are derived from PDO so if you are familiar with that, you will have no problem transitioning to DBTNG.
Drivers in DBTNG are in charge of taking the base statement built by the user and transforming it into a SQL statement that is valid for the database you are working with. Each database type must have a driver built for it to work with Drupal 7. The default installation includes drivers for MySQL, PostgreSQL, and SQLite. Other drivers may be available after release as custom modules or patches.
Drivers are installed in the includes/database
directory of your Drupal installation. Each driver is given its own sub-folder, which should be named based on the database name and it should typically only contain lower case letters.
Drivers typically consist of four include files that contain classes which override core database functionality. These include: