What will happen if I remove "essential components" for Gnome?

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http://askubuntu.com – I'm using Ubuntu 11.10 with Gnome 3. There are some applications that I don't use or need, for example Totem. When I click remove in the Software Center (or in Synaptic), it says "gnome-core" and/or "The gnome desktop environment - essential components" will be removed as well. I removed these applications about a month ago by ignoring the prompts and once I restarted, Ubuntu would not load and would simply sit there at the loading screen. I'm not sure if removing gnome-core caused this issue, but I really want to remove some of these applications. What is gnome-core and how do I know what (HowTos)