Numbers and Details
To begin with, think of the aperture of your camera lens as the size of its opening. The photons of light arrive to the lens and are focused by the lens onto the sensor. The sensor records and translates the analog signal into digital numbers, which then get written onto your memory card. The numbers that describe the aperture of our lenses are typically these:
F/1.2, F/1.4, F/1.8, F/2, F/2.8, F/4, F/5.6, F/8, F/11, F/16, F/22, F/32, F/45
As the number gets smaller, the opening of your lens becomes larger, which means more light enters your camera. The larger the number gets, the smaller the opening of the lens becomes and therefore less light enters your camera.
The reason why the opening gets larger with smaller numbers is because those numbers, also known as F stops, actually represent fractions of the numbers. For example, F/1 represents the full diameter of the lens you have divided by 1, which equals the entire diameter. So a theoretical lens that could have an aperture of F/1 would in fact be fully open. F/2 means the full diameter of the lens divided by 2. If you have a 50mm lens and you set the camera to, the opening of the lens will be 50/2 = 25mm. Although you have increased the number by going from F/1 to F/2, the opening of the lens has decreased from 50mm to 25mm since the F numbers represent a fraction of the diameter of the lens.
In the same way, F/8 in a 50mm lens would mean 50/8= 6.25mm. Therefore, the opening of the 50mm lens gets smaller and smaller as we increase the F numbers of our aperture settings.