The aperture, also known as the F stop, simply means ‘opening’. It is the size of the lens when the photograph is taken, allowing light to pass through.
Changing f-stops on your camera will halve or double the amount of light that is let in, this is where is works in combination of the shutter speed. If you have increased your shutter speed then you’re letting less light in so to compensate you need to have a larger aperture.
Just to confuse new photographers, the large apertures (lots of light getting in) are given small f numbers and small apertures (less light getting in) are given big f numbers. so f/4 is much larger than f/22.