Workspace vs --library?

I've been using the --library option of Darktable for years to specify a custom path to the database file.

How is this option different from the new Workspace functionality?

https://preview.redd.it/q0ji8wls6y0h1.png?width=1316&format=png&auto=webp&s=5b7b1e3288516856888768e06aae746d7adfa849