In short, it's a terminal multiplexer (hence the name, tmux) that allows you to run multiple terminals within one (as opposed to opening a new window for each interactive shell you want to use). I spend 90% of my time as a developer either inside tmux or a web browser, so it wouldn't be a stretch to say that I find it quite useful.

The functionality I use the most in tmux is:

- attaching and detaching from a tmux session (e.g., for running machine learning jobs over SSH)

- having multiple terminals open inside of one

- scripting the setup of windows, panes, etc. for different projects I'm working on

I basically use vim and tmux as an IDE: my usual setup consists of one large pane consisting of vim and code, while two other panes are available for running git commands, starting servers, etc. Within one tmux session I separate different projects (e.g., frontend and backend) into tmux windows, and it's very easy to switch between panes, windows and sessions using keyboard shortcuts.