The term pixel is short for "picture element". In short, it's a single dot, and your image is made up of a grid (2 dimensional matrix) of pixels. Each pixel contains a finite amount of information and not all pixels are created equal. Hence the term, "pixel depth", which specifies how many bits each pixel contains. If you think of each pixel as a little container, pixel depth specifies the size of the container. In video, some pixels contain color+brightness information, and some contain only brightness. That is to conserve bandwidth, storage, etc. It's a form of compression.
So, an HDV 1080i camera will have a pixel resolution of 1440x1080 which is about 1.5 million pixels (by comparison, standard definition has about 350 thousand pixels). The pixel depth in HDV is 24 bits for color pixels and 8 bits for luminance (brightness only) pixels. Color information is stored in 1/4 of the pixels, so the color resolution is only about 400 thousand pixels, and it is highly compressed.
The reason a high end video camera, like a Varicam can produce a much better standard definition image is because it stores more color information than a miniDV standard definition camera.
What I'm trying to say, is that pixel resolution is not the entire store. It is true that higher numbers of pixels gives you more image detail and therefore will display better in a larger format. However, a high end HD camera will store a lot more image detail in the same number of pixels, producing a better picture than an HDV camera; even at identical resolution (pixel count).
Finally, when purchasing a camera, you need to know that not all cameras using the same format and resolution are created equal. Video is heavily processed before being stored to tape, disk, etc. First and foremost, you can only record an image a detailed as the camera lens can resolve. Trust me when I say that not all lenses produce the same quality image. Next, the quality of the image sensor (CCD/CMOS sensor) determines how well the light is captured at the first stage. Sensors have all sorts of advanced features that help them collect light, separate colors (sensors only detect brightness, so something must be done to separate and record color values). Beyond the sensor is all of the electronics that harvest, analyze, enhance and compress the image. Finally, the image is stored somewhere (tape, hard drive, solid state storage, etc.). Generally the amount of compression is determined by how much information can be stored. In the case of HDV, the image cannot exceed 25Mbps (25 million bits per second) if it's going to be stored on a miniDV tape with a standard (cheap) DV tape deck.
Professional cameras use better lenses, better sensor technologies, faster and higher quality electronics, and often have faster storage systems (hard drives, or solid state storage) that allow them to retain more image information.
Prosumer cameras use inexpensive miniDV mechanisms (most of them), but generally have better lenses and better electronics than consumer cameras. They also give you more options for connecting gear and controlling your image.
Consumer cameras often use cheap glass and fewer elements in their lenses that causes more chromatic distortion and poor image resolution, in spite of the "high definition" designation. A lens can only resolve a certain amount of detail. 35mm cine lenses are extremely expensive, and one reason is that 35mm resolution requires high quality optics (there are other reasons, also, that I'm just going to gloss over for now).
Hopefully I helped with your question. I apologize for all the extra detail, but you or someone else might find this information useful. Someday I'm going to construct a web page with images shot on the same camera with different lenses of varying quality, so I can visually show what a big difference a lens can make, when everything else is equal.
Doug
i know its the miniature dots or lines that make up the picture... i mean how does this effect your video?
