A terminal multiplexer.

Leader

I use C-G on workstation and laptop and C-B on server and media center.

Using C-G is less of a reach than C-B when using CAPS LOCK as CTRL.

Manage nested tmuxes by repeating the leader, e.g. server-within-a-server via C-B C-B.

As an "IDE"

A 1920px wide full-screen terminal using Ubuntu Mono 10pt (7px/ch) provides a width of 274ch. This is enough space for two columns of full-width vim and a third column for a usable shell. See workon.