tmux status line

The status line gives you information about the session and window you are currently viewing, which other windows are available in this session, and more.

It can be customized. These customizations include things that are a part of tmux (such as the time, date, server you are connected to, and so on) or things that are in third-party libraries (such as the battery level of your laptop, current weather, or number of unread mail messages).