The Aperture is a feature of the Camera which is linked to the sharpness of the final image. The setting may blur the background of the photo by focusing on the foreground or bringing the entire scene into focus. This is dependent on the dimension of the Aperture, which is the entrance point of light for the lens of your Camera. This restricts what light enters the Camera.
The dimension of the Aperture, open or closed, determines the amount of light that can be absorbed through the Camera. This is measured using F-stops like f/4.5. The smaller the f stop the greater the Aperture. A big Aperture produces a photo that has a blurred background, and a smaller Aperture will bring everything in the image into focus.