Ecaml.Selected_windowSourceThe selected window is the one that you edit in. When a window is selected, the buffer in the window becomes the current buffer, and the cursor will appear in it.
(Info-goto-node "(elisp)Selecting Windows").
(describe-function 'select-window)
(describe-function 'switch-to-buffer)
(describe-function 'switch-to-buffer-other-window)
(describe-function 'split-window-horizontally)
(describe-function 'split-window-sensibly)
(describe-function 'split-window-vertically)
(describe-function 'find-file)
(describe-function 'find-file-other-window)
(describe-function 'view-file)
(describe-function 'save-selected-window)
(describe-function 'with-selected-window). Avoid using set_temporarily, which can have visual artifacts that annoy the user, like flicker of the mode line or cursor.
(describe-function 'save-window-excursion)
(describe-function 'quit-window)
(describe-function 'other-window)
(describe-function 'window-height)
(describe-function 'window-width)