What is Gingerbread?
It is a new version of the Android OS released by Google. It has a version of 2.3 compared to 2.2 currently on the Ideos.
Why is this better?
Because Google has done a lot of work on it especially the interface and the keyboard but speed tweaks as well.
So how does CM relate to this?
CM are tweaks built upon the underlying Android OS which make it much better. A lot of new options and speed is added but the most exciting feature is the T-Mobile theme Engine. This allows the user to completely modify the appearance of the phone with no performance reduction or stability reduction It is also extremely simple and easy to use.