What is the F-number?

The earlier specification also had a F-number,
Lens aperture - F/3.5-5.6
This is another interesting number, although u don't have to worry about it much. It just says the size of the aperture under two situations - fully zoomed out (no zoom) and full zoom. Smaller number means bigger aperture. It starts with F/1.0. Bigger aperture is better. And lenses that stop at 3 points of there minimum generally perform better.