Shell---- Window Manger Dilemma

What is the difference between a shell and a window manager like ratpoison?
what makes bash a 'shell'
but
ratpoison a 'window manager' ??

What is the difference between a shell and a window manager like ratpoison?
what makes bash a 'shell'
but
ratpoison a 'window manager' ??

From Ratpoisons Website

Ratpoison is a simple Window Manager with no fat library dependencies, no fancy graphics, no window decorations, and no rodent dependence. It is largely modelled after GNU Screen which has done wonders in the virtual terminal market.

Read this too *www.gnu.org/software/screen/

......When screen is called, it creates a single window with a shell in it (or the specified command) and then gets out of your way so that you can use the program as you normally would. Then, at any time, you can create new (full-screen) windows with other programs in them (including more shells), kill the current window, view a list of the active windows, turn output logging on and off, copy text between windows, view the scrollback history, switch between windows, etc. All windows run their programs completely independent of each other. Programs continue to run when their window is currently not visible and even when the whole screen session is detached from the users terminal.

Further I think the only two people who actually have used ratpoison is Mehul and Hullap.