Emacs frequently has more than one window open, and
C-x o can be used to switch between them.
C-x o is far less useful when you have three or more windows open, since you need to use it multiple times to reach the desired window. The Ace-Window package improves this situation by allowing you to navigate directly to a window.
(use-package ace-window :ensure t :pin elpa :diminish :bind ("M-o" . ace-window) :config (setq aw-keys '(?e ?t ?u ?h ?o ?n ?i ?d)))
I've bound the keys for different windows based on the Dvorak keyboard layout that I use with my Kinesis Advantage keyboard, prioritizing the strongest fingers. The effect of this package can be seen below: