The exposure triangle
Now you have learned the basics about aperture, shutter speed and ISO which often are referred to as the exposure triangle and together creates the exposure for your photos. The settings affect the brightness of the image and understanding these fundamental settings is key to any photographer so I hope you learned from the above. The only way to master it though is to get your gear out and practice. Photographer Tony Catalano has created an interactive exposure tool which is great for understanding how aperture, shutter speed and ISO work together to create the exposure value.
Another way to look at the exposure triangle is with the faucet analogy: Say you need X amount of light to create a perfect exposure, or in this analogy, X amount of water. How much you turn the handle (flow rate) resembles the aperture, the time of which the tap is on resembles the shutter speed and the size of the container to be filled resembles the ISO. This analogy is explained by Pye Jirsa from SLR Lounge in the video below.