The more pixels you have, the sharper your image will be. The smaller number, called optical or high-definition zoom, is how far the camera lens itself can blow up the picture. The other, called digital zoom, is how far the camera's computer can blow up the picture using the original image and software. Because digital zoom doesn't gather additional information about what's in the video, it doesn't give you images as sharp as optical. That means something you blow up to 300 times normal size will likely be fuzzy.
Sharp cameras tend to have just the screen.
The larger the screen, the easier it is to see whether your subject is in focus. Often, viewfinders on cheaper models are black and white only, so if you think you'll be using that rather than the screen, go for a more expensive model. All newer digital video cameras allow you to connect to a TV or VCR using S-Video cables that usually are included. That means you can play back your videos on TV or record them on standard VHS tapes. All cameras will play back your videos on their own screens.