These are responsible for presenting your Desktop to you. In simple terms, it does the function of explorer.exe in Windows. There are many types of desktop managers. Some popular ones are GNOME, KDE, CDE and XFCE. Each has its own advantages and disadvantages.
The window manager is responsible for the looks of your Desktop. It is like the theme manager in Windows. Every window manager has its own unique feature. Some like compiz and beryl are definite eye candies. They have several inbuilt features like animations etc.
Ubuntu uses GNOME Desktop Manager with Compiz Window Manager. However, these can be changed to our need.
To know more about any desktop manager or window manager do a simple GOOGLE search. I will post a list of the popular desktop and window managers along with the link in my next blogs. Till then, c ya!!!