Hi dappledesigns. When shooting indoors you would need a fast lens. When I say fast lens, I mean a lens with a large aperture. The wider the aperture, the more light will enter the camera, meaning you will be able to get faster shutter speeds. By getting faster shutter speeds, that means you will avoid getting "shaky" photos.
For wedding photography, I would recommend prime lenses, (lenses that do not zoom in or out) like a 35mm, 50mm and 85mm. Prime lenses are usually cheaper than zoom lenses and come with wider apertures.
The lower the number the bigger the aperture, so more light.
Look for a minimum of f1.8 on the lens.
Any wider than that and the lens will end up being very expensive. If you have any questions please feel free to contact me.
There are lots more to talk about when it comes to lenses, but I recommend you take a beginners course in photography, where you can learn to make the most out of your equipment.