The D7000 is an entry-level DSLR, and
very suitable for someone new to DSLR cameras. In fact, the D7000 is the most capable of Nikon's current, 6 entry-level DSLR offerings - D3000, D3100, D3200, D5100, D90, D7000.
Any camera body can only be as good as the lens that is mounted on it.
Nikon makes 3 grade levels of lens: consumer grade, prosumer grade, and professional grade.
The basics are that consumer grade lenses have smaller maximum apertures (f/3.5 is a smaller aperture than f/2.8 is), and a somewhat lower build quality than the prosumer and professional grade lenses. Smaller maximum apertures hinder shooting in low light situations, and make it a bit more difficult to use selective focus techniques that make a background blurry. (Note: The smaller the maximum aperture, the less light it can let into the camera.)
To keep the costs lower, consumer zoom lenses have a variable maximum aperture. A typical kit lens is an 18-55 mm f/3.5-5.6 zoom lens. Those number mean that the maximum aperture when the lens is set to the 18 mm focal length, f/3.5 is the maximum aperture you can use. as the lens is zoomed towards 55 mm the maximum aperture you can use gradually gets smaller until it is f/5.6 just before you get zoomed all the way out to 55 mm for the focal length.
The prosumer and pro grade zoom lenses usually have a more expensive to make, constant aperture like a 24-70 mm f/2.8 designation. If the lens is set to f/2.8 at 24 mm and then zoomed towards 70 mm the lens aperture does not vary and stays at f/2.8 through the entire zoom range.
Consumer grade, variable aperture zoom kit lenses - ($450):
Nikon 18-55mm f/3.5-5.6G AF-S DX VR Nikkor Zoom Lens
Nikon 55-200mm f/4-5.6G ED IF AF-S DX VR [Vibration Reduction] Nikkor Zoom Lens
Or - ($399)
Nikon 18-105mm f/3.5-5.6 AF-S DX VR ED Nikkor Lens for Nikon Digital SLR Cameras
Nikon budget trinity of constant and variable aperture zoom lenses - ($2880):
Nikon 12-24mm f/4G ED IF Autofocus DX Nikkor Zoom Lens
Nikon 24-85mm f/2.8-4.0D IF AF Zoom Nikkor Lens for Nikon Digital SLR Cameras
Nikon 80-200mm f/2.8D ED AF Zoom Nikkor Lens for Nikon Digital SLR Cameras
Nikon Professional Trinity of constant aperture zoom lenses - ($6300)
Nikon 14-24mm f/2.8G ED AF-S Nikkor Wide Angle Zoom Lens
Nikon 24-70mm f/2.8G ED AF-S Nikkor Wide Angle Zoom Lens
Nikon 70-200mm f/2.8G ED VR II AF-S Nikkor Zoom Lens For Nikon Digital SLR Cameras