Driver
In the context of dbc, "driver" means "ADBC driver." It's ADBC drivers that dbc lets you install and manage. ADBC is part of the Apache Arrow project and is a free and open standard. dbc builds on top of it.
Note
What an ADBC driver actual is is entirely defined by the ADBC project, so we'll give a simple definition and then refer you to the ADBC project itself if you're interested in going deeper.
What Is an ADBC Driver?
At a high level, an ADBC driver is a library that wraps the client for the database you want to use and exposes that database to you with a consistent API: the ADBC API.
For example, if you're using the ADBC SQLite Driver in C++ code and you want to run a SQL query, you'd call two functions (in order):
Inside the driver, these two functions call corresponding functions in the SQLite API:
While there's no hard requirement for a driver to have a 1:1 correspondence like above, hopefully it helps explain that there's no magic.
More Resources
If you're interested in learning more about ADBC drivers or ADBC, check out these two pages: