What does the lens on a DSLR camera do?

Is the lens used for zooming in or for focusing on objects when taking pictures or both? Do all lenses focus and zoom, if both? What does the Nikon D3200 lens do?

1) The lens forms the image (a camera body without a lens will produce a simple, undifferentiated grey image).

2) All lenses focus - allowing the final image to be sharp (control of focus (differential focus) and how much of the final image is sharp (depth-of-field) are among the most difficult (and rewarding) elements of photography to master).

3) Not all lenses zoom, and not all zooms mean the same thing. A 50mm (one focal length figure) f1.8 can't zoom, an 18-55mm (two figures and a dash) can change its angle of view from landscapes to portraits depending on what's required.

4) Modern DSLRs focus automatically (half depressing the shutter release allows the camera's built-in system to focus on what you're pointing at), this can be over-ridden if you know what you're doing.

5) The lens hasn't been made that can do every job. Most entry-level DSLRs come with an 18-55mm standard zoom, because it's cheap, light in weight, easy to use, and an excellent place to start answering these questions for yourself.

The lens focuses the image on to the sensor (or film) and ensures you get a sharp image.
A zoom lens enlarges or reduces the image as you turn the zoom ring; nothing to do with focusing. A prime (non zoom) lens is not able to enlarge or reduce the image; it shows one angle only when you look through it.

It channels light into the camera. All lenses focus and some zoom also but the very best optically do not zoom.

http://keerok-photography.blogspot.com/2012/03/shoot-dslr-without-lens.html

The same as the lens in any camera - it focusses the image. Only pinhole cameras do not have lenses of some sort.