DSLR lenses when to use 18-55mm and 55-200mm?

I'm completely new to dslr cameras and I'm hoping to buy one soon. I've been looking online and notice that most deals come with 18-55mm but then one that i'm really interested in comes with 18-55mm as well as 55-200mm. It's the Nikon D3100 that I'm looking at (http://www.jessops.com/online.store/products/81730/show.html). Some also say VR, IS (etc) so confusing.

When would I use each lens?

Sorry if this sounds completely ridiculous.

I'm a professional photographer.

The D3100 is DX (small sensor) camera, not FX (full frame)

When I'm shooting indoors on my DX (D300) camera, my 24-80, 2.8 is great. I wish it were 20 to 95, though.

When I'm outside, I would want the 55-200mm. I use the 70-200 2.8, and I get incredible shots. I have a book coming out, it's all portraits, and they were all shot outdoors with that 70-200.

I shoot mainly people - portraits, weddings, family gatherings.

If you want to shoot scenery, you probably want the 27-80.

I would guess that either lens that is sold with the camera is mediocre. You might want to do some research. Consider getting the 24-70 2.8

Don't worry about what those terms describing the lens. VR, means vibration reduction and this information is available on the Nikon website.

The 18-55 mm lens covers landscapes, group shots, full body shots and head and shoulder shots.

The 55-200 mm continues from the head and shoulder shooting range to the ability to shoot sports, action and even some wildlife.

18-55mm and 55-200mm are the focal lengths of the lenses; right about now I guess that means nothing to you. The focal length affects the Field-Of-View, the smaller the focal length (18mm on the first lens) the wider (and taller) the view the lens sees. The greater the focal length the narrower and shorter (in height) the view the lens will see.

You see an interesting tree in a stunning vista, if you use the 18-55mm lens at it's widest setting (18mm) you could capture most of the landscape laid out directly before you. If you now switched to the 55-200mm lens and went to the other extreme you would just see the tree, or even the birds in that tree filling the whole of the viewfinder on your camera.

*I'm a technologist (among other things) which means I see (and think about) things differently than many people.

No, it's a good question to ask. You should understand what focal lengths are for what.

Your 18-55mm lens will be the one that gets more use, it's a general purpose lens. 55-200mm is a telephoto lens, it gives you some extra reach, however I think this lens is not the most useful in the world. There isn't a great deal that this range brings you, the 55-200 is not long enough, and neither is it fast enough.

Here's a rough guide to what the different focal lengths are useful for:

Less than 24mm - Landscapes.
20-30mm - Environmental portraits, documentary photograph (usually with primes)
35-85mm (fast, e.g. Around f2-2.8) - Traditional portraits
85-135mm (fast, around 2.8) - Headshots
200-400 - Sports
300-800 (and more) - Wildlife

Your 18-55mm is a great walkabout lens, and works well for wide view, and for subject not too far away. The 55-200mm continues and brings subjects much closer, depending on what focal length you zoom it to.

Here's a Nikon Lens Simulator that will allow you to see the effect. Choose the picture/scene you want, then slide the indicator at the bottom.
http://imaging.nikon.com/...simulator/

P.S. VR and IS (Vibration Reduction for Nikon & Image Stabilizaton for Canon) do the same thing. They help steady the lens and camera to reduce motion blur.

As for beginning I suggest 18-55mm lens which is versatile and really useful in most situations.