Byobu is an enhancement for tmux and GNU Screen that provides text-based notifications and tabbed window management.
Quote from the Wikipedia article on Byobu (software):
Byobu is an enhancement for the terminal multiplexers GNU Screen or tmux that can be used to provide on screen notification or status as well as tabbed multi window management. It is aimed at providing a better user experience for terminal sessions when connecting to remote servers.
Byobu was previously called screen-profiles and was originally designed to provide enhancements to GNU Screen. Byobu 5.0 switched from GNU Screen to tmux as the default backend, which is supported since version 4.0.