Depth of field (DoF) is the distance between the nearest and furthest elements in a scene that appear to be “acceptably sharp” in an image. Mastering depth of field will give you the creative control over what’s in sharp focus in your images, turning you into a better storyteller.
Aperture is how you will change the Depth of Field. Use large apertures for a narrow DoF and small apertures for wide DoF. You need to know that aperture effects other elements, too. A large aperture lets in more light than a small aperture.
Large aperture (small F/stop) = Narrow Depth of Field
Small aperture (large f/stop) = Wide Depth of Field