Aperture is the size of the opening in the sense of a camera which controls how much light is let into the lens. It also controls something called depth of field, which is the range of focus in an image. The lower the aperture number is, the more focused it is on one particular object (the smaller the focal point is), and the bigger the aperture number is, the wider the focal point will be (more of the photo will be focused rather than a tiny part of the image.
In this image, the photo on the left has been taken with f1.8, which means the focal point will be more narrow, which is why the gnome in the image is really focused and the rest of the image is blurred and unfocused. The image on the right has been taken with an aperture of f22 which means that the lens will have been opened up wider for it to have been taken, this also means that the focal point will have a wider range, which is why a most of the photo is more clear rather than the other one.
These are my photos i have taken which shows the same image taken at the aperture of F2.2, F10, F22. The photo taken in F22 is all focused and there aren’t really any blurry parts. F10 begins to show focal points, but F2.2, the smallest, shows a strong and specific focal point and all the rest of the image is blurred.