This Hubble image of NGC 3372 (Carina nebula) is composed of 50 single images. The brightest star by far is Eta Carinae, centred vertically and at about 20% of the image width from the left. The image contains part of the Carina nebula; the distance from the left to the right of the image is approx. 50 light years. The false colours indicate some of the different elements of which the nebula is composed: green is hydrogen, blue is oxygen and the red parts contain sulphur. Sun.org also has another image of the Carina nebula with more information about it.
If interested, read more about: Emission nebula - Reflection nebula - Molecular Clouds and Dark Nebulae