The text you are editing in Emacs resides in an object called a buffer---any changes you make are saved in the original file only when you save the buffer. Emacs allows you to hold many buffers-in-waiting while you work on one (and only one) buffer, the selected buffer. When Emacs makes multiple windows, each window contains a buffer, but only one window can contain the cursor at a time. Most Emacs commands operate only on the selected buffer.
Emacs also has a `Buffers
' menu which allow you to switch
between buffers at the click of a mouse button.