This tool is a dark theme option to be added to your GNOME desktop.
GNOME is an international endeavor aimed at creating a comprehensive desktop environment that is built entirely from free software. This objective includes the development of software development frameworks, application software selection for the desktop, and managing programs that deal with application launching, file handling, and window and task management.
GNOME is part of the GNU Project and can be utilized with various Unix-like operating systems, homing in on Linux and as part of Java Desktop System in Solaris. Though the acronym has now been deprecated, the name originally stood for GNU Network Object Model Environment. The GNOME Project advocates for simplicity, usability, and "just works" when it comes to accomplishing tasks within the environment.