Tabs in Emacs master
For those who are not familiar with Emacs, a buffer is a file, something that isn’t saved to a file yet or some other thing like an interactive UI. But a buffer can be open without being visible in the UI. This is very different from most editors. Some other details you should know is that what most people call a window is called a frame in Emacs, and a frame can be divided into multiple windows.
There are two different types of tab bars in emacs 27. One is per frame and the other is per window.
The per window tab bar just shows buffers you open and let you switch between them, close them (without closing the buffer). This is called tab-line-mode. While the per frame tab line let you switch between frame configurations. A frame configuration is just how you have split and resized the windows in your frame.
It currently looks like shit. Seriously. It looks horrible. But I think this is a great change that makes a lot of stuff much easier to do in emacs. Especially if you have a lot of buffers with different stuff that you want to organize in different ways.