I understand your confusion.  It's a badly-worded package name."ubuntu-desktop" is what they call a meta package.  it doesn't actually contain anything.  If you uninstall it, nothing happens.That package just requires every package in the default install.  If someone were to install that package, they would get the whole default software install in one click.  But uninstalling it is not dangerous.So go ahead, remove Open Office if you want. :)

When you put in the CD, you're starting a demo of Ubuntu. It's not installed yet. To actually have it on your machine you have to install it, the same as Windows or any other Operating System.

After Ubuntu is installed, you'll find it came with several other pieces of software which may people find useful. Just because they came in the install doesn't mean you have to keep them. You can just uninstall them if you don't want them. There may be ways to control what gets installed during the OS installation, but I don't know how, sorry.

If you click System -> Administration -> Synaptic Package Manager and look for the entries for Open Office, you should be able to simply uncheck them to uninstall Open Office.

When Ubuntu starts, you begin on the desktop, so you wouldn't need an icon for it. Under gnome, the icon at the bottom left corner clears all windows from the desktop, if that's what you need.