A photograph of a single object is a case where we want to get all the focus in the photo on the object while we want to reduce all other pars so that they do not interfere with our object. This is often done using a blurred background and you see this very often in portrait photography.
When taking a photograph the f-value we set the camera on is often used to blur or not blur the background. It is easy to think that to get that beautiful blurred background we just need to set a small f-value and we’re done. This is however not the entire thruth.