Windows

Emacs allows you to open multiple files at once, or open irc in emacs while editing, which is very helpful. You can open a new one using C-x 3 (split-window-right) or C-x 2 (split-window-below)

You can also use C-x 1 (delete-other-windows), which does exactly as it says it does, and deletes the other windows.

You can also use C-x 4 f to open a file in the other window. It calls the function (find-file-other-window)