Welcome to Cobl (Common Oblivion)! If you downloaded Cobl for itself, then you'll find that it significantly enriches the world of Oblivion: new races, new books, new ingredients, new foods, etc. There are no quests, but you'll find the world a better and more interesting place in many small and large ways.

If on the other hand, you downloaded Cobl because some other mod required you do to so, then... You'll still find the world a more interesting place! But you'll also get the benefit of having multiple mods work better together, and be richer, more powerful mods in themselves.