Aperture is the opening in the lens that is made up of a series of overlapping blades and controls the amount of light that enters the camera. It is measured in f-stops and depending on the lens, it can range from f/1.4 to f/32. Each f-stop doubles or halves the exposure of the photo. The lower the f-stop value, the larger the opening in the lens and vice-versa.
The aperture also controls the depth of field in your images. The depth of field refers to how much of your shot appears to be in focus and how much is blurred. The lower the aperture value, such as f/1.4, the shallower the depth of field, and hence the stronger the background blur. Incidentally, the higher the aperture value, such as f/32, the wider the depth of field becomes hence a sharper background.
A shallow depth of field is great for portraitures and macro photography as it lets you focus and direct attention to your subject, while a wider depth of field is great for landscape and architecture photography, allowing you to capture all the nuances of the scene.
Aperture can also affect the shutter speed. Using a lower aperture value such as f/1.4 means that more light is entering through the lens, therefore the shutter speed doesn’t need to remain open for a long time to obtain a correct exposure. On the other hand, when using a higher aperture value such as f/32, less light is entering through the lens, so you will need to use a longer shutter speed to ensure your image is not underexposed.
Experiment with different aperture settings to see how they can express your creative vision.