Graphical environments on Linux can basically be divided in two main groups: full-featured desktop environments such as GNOME, KDE Plasma or XFCE, and barebone, minimalistic window managers, such as i3, openbox, or sway. The former come with a set of applications and utilities designed to work well together, while the latter are meant to perform just one task (or little more): managing windows. When using those environments additional functionalities must be implemented via separate tools.
I3 is one of the most used tiling window managers on Linux. A tiling window manager arranges windows in a non-overlapping way: this allows us to use screen space efficiently, but can require a little bit of time to get used to.