Canon Eos 7d Digital Camera
What are pixels? especially in digital cameras?

I was looking at a Canon (EOS 7D) online and says it has 18.0 pixels, my camera right now has about 12. What is the difference? and how it will impact image quality and so on.?

PIXEL is short "Picture element" and means little minute individual bits of the image are composing the image. With the film of the pixels are formed using bits light-sensitive chemicals, with digital each pixel is a tiny electronic light sensor that combines with all others in the sensor array to capture light / color, etc, which makes the image. To some extent, the greater the number of pixels, the better quality, but of course, is not that simple. It also depends pixel size, how close the other pixels (crush together is not good, but neither is taking too large a) difference how good these pixels are in the capture of information and how well the information is processed by the computer from the camera. You see the camera manufacturers to announce their image on board processing software as often as they do with their lenses and ISO sensitivity range. And so on. In the end, talk to sales staff in a good camera shop, try different cameras and see what you prefer to shoot at the price you want to pay. If you get stuck, you can always ask, and good luck.

Canon Eos 7d Digital Camera

is the Canon EOS Digital Rebel (the name exactly, not 7D, etc.) a full-frame camera? or ASP-c?

Rebels complete series device photo (or # # # EOS D-series in Europe) has sensors APS-C. They also have APS-C size sensor EOS 40d, 50d, 60d, 7d. Camera full size Canon EOS 1D and EOS 5D.

Which?: Canon EOS 7D UK launch