By default, using ‘C-x C-b’ will call ‘list-buffers’ with BufferMenu. The list of buffers is displayed in another window. If you want to use it in order to switch buffers, you will have to hit ‘C-x o’ to switch windows, first. This is a very crude way of switching buffers.
The following code will eliminate the need for ‘C-x o’, making list-buffers much easier to use:
(global-set-key (kbd "\C-x\C-b") 'buffer-menu-other-window)