Weboob is a project which provides a core library, modules and applications.
Each module interfaces with a website and implements one or many of these capabilities. Modules can be configured (becoming a "backend"), which means that the end-user can provide personal information to access the underlying website, like a login and password.
Applications allow the end-user to work with many modules in parallel, in a multi-threaded way. For example, one could search a video on many websites at once. Applications are toolkit-agnostic. They can use GTK+, Qt or be text-only. The latter can be used either in an interactive way or in pipes.
The core library provides base classes which help developers write modules and applications.
Weboob is written in Python and is distributed under the AGPLv3+ license.
For more information, please go to the official website.
Some extra info is available in the Gitlab wiki.
If you are a developper and looking for how to write a module or contribute to Weboob, you can have a look at the developper documentation.