If it is an ordinary digital camera for home use, it will be simple. First ask how many times the optical zoom is (many businesses confuse digital zoom with optical zoom). The bigger the optical zoom, the better the machine. For example, ten times optical zoom is much higher than three times and five times the price. Second, the higher the pixel, the better the machine. It is good to have a family number of120,000 or more. The proposal of less than10 million is out of date. You should know other accessories such as batteries and memory cards.
If it's a SLR camera, it's much more complicated, and I can't explain it clearly later.