First off, you've installed gnome-the-package, not gnome-vis-a-vis-the-gtk-api or gnome-the-user-desktop or gnome-the-{insert other ideas here}. There is a difference; some of these are ideas and concepts, some are software, some are development tools, and some are just there for the systems administrator.
I think you are also confusing several concepts. Unlike what you find in Windows (where one-size-kinda-fits-all*), your Linux environment is much more modular and can be heavily customized. The parts needed are installed in layers, with a display, a display manager, a window manager, and on top of that any user programs.
A Quick Visit to X11 and Friends
X11 is a graphical display environment, in the form of a server, a client, and a protocol. Graphical sessions can either be local to a video device, or over a network to a remote client. Using X11 allows you to isolate where you have your graphics appear from where they originate from.
A display manager's job is to provide authentication (a graphical login screen) to determine who is and isn't an authorized user, and launch the appropriate graphical session for that user. Display managers can be thought of as a kind of gatekeeping process for X11, asking users to identify themselves and managing who gets access to what display (where I'm using display to loosely describe your X11 session).
After the display manager has determined who you are and what you want to do (or should be doing), it then launches various programs, usually including the window manager. The window manager's job is to do what it sounds like - manage windows! If you ever get to a point where your windows suddenly loose all their borders and you can't resize them, then the window manager has stopped working.
When people talk about desktop environments in linux, what they are usually talking about is actually a collection of several things, including X11, a display manager, a window manager, and several user programs, all installed together to provide a "desktop experience". When you install "Gnome", you're really installing gdm (the Gnome Display Manager), Metacity (a window manager), and a boatload of other programs to provide a "desktop experience".
Because every user is different, and some users will have different expectations from others, there are usually a broad swath of programs that cover a majority of use cases, so that people can start using it right away. That's why when you installed gnome, you ended up with all kinds of stuff, and not all necessarily stuff you wanted.
That being said...
When you install a package in Debian, you are potentially installing other packages that are dependencies, i.e. these other packages need to be installed 'underneath' it for the one 'up top' to function properly. When you installed gnome-desktop
as a package, you installed a variation of this, a meta-package, which is a package of nothing but dependencies on other packages; the gnome-desktop
package doesn't itself have any thing really in it (other than a few glue files), but rather, the dependencies attached to it cause all of the others to be installed.
If you are looking for a minimal GUI environment, and want to control what is and isn't installed to keep things lightweight, you're better off uninstalling gnome-desktop completely, purging all of the files in the process, and then re-installing something smaller with no dependencies. You'll need to leave your GUI behind for a moment, because the package tool you're trying to use may or may not be a part of the removal process; so you'll want to get into a normal text shell, probably by pressing Alt-F1 while at the system console. From there, log in as root, and do the following command:
apt-get purge gnome-desktop && apt-get update && apt-get install fluxbox
That command will remove the gnome desktop and all of the associated packages, update your list of available packages to install, and install fluxbox
as a window manager. After installing your window manager, you'll want to install other software that uses a GUI interface and proceed from there; most likely you'll want to do the following as root while in that shell:
apt-get install synaptic && /etc/init.d/gdm restart
That will install the synaptic
package manager and restart your display manager. From there, log in, and run synaptic from the menu of your window manager, and select the packages you want to install. Be sure to not re-install gnome-desktop
again.
*Footnote: yes, I know that Windows uses modular components itself, and that several can be replaced as needed; but in practice, and from the general public's point of view, it's usually seen as a monolithic entity, with a single user interface.