The meaning of aperture is – “A  space through which light passes in an optical or photographic instrument, Especially the variable opening by which light enters a camera.”

Aperture is measured in ‘f-stops’. The smaller the f-stop the more amount of light is allowed in, and the larger the f-stop, less amount of light is allowed in. 

The meaning of depth of field is – “the range of distance that appears acceptably sharp.”

Large depth of field means that most of your image will be in focus whether it’s close to your camera or far away. The larger the f-stop, the larger the depth of field will be.

Small (or shallow) depth of field means that only part of the image will be in focus and the rest will be fuzzy.The smaller the f-stop, the smaller the depth of field will be.

The image bellow was taken with a medium aperture, around 16 f-stop,  because the person in the foreground is in focus where as the objects in the background are blurry.