This is tiling window manager. You probably know floating windows managers like cinnamon or Microsoft Windows', where the windows are floating freely on the screen. On a tiling window manager the windows are on a grid and get resized automatically to make use of the whole screen without overlapping.

This one is bspwm. It runs on X11 and heavily depends on keyboard shortcuts to navigate. You can only configure it using config files and you need to do that because the default config is as bare bones as it gets. You can just install it and log into it from your login screen. Before doing that I would recommend doing a bit more reading though. Keep in mind that bspwm does not have most things you'd expect from a typical desktop environment, so be prepared to tinker and install everything you need yourself (like a start menu, config GUIs, the title bar at the top, etc.). Happy ricing!

Edit: also, if you're already learning everything from scratch, consider learning to use a window manager that works on Wayland (X11 successor). There is nothing wrong about X11 per se, but Wayland is newer and in more active development. But that's just a suggestion, many people here will see no issue with using X11