Amongst other things, the f number affects the depth of field (how much of the image is in focus.
A low number (f/1.6 is fairly low. f22 is fairly high) means that only the object you focused on will be sharp and anything nearer or further away will become blurry. This is great for portaits for example as it draws attention to the person.
(f is the aperture and also affects the amount of light. You can shoot with a lower shutter speed if you have a wide aperture/low f number)
The "mm" number is the amount you're zoomed in. Wide is a low number, telephoto from a distance is a high number.
But blur can come from other things. Cheap lenses, unsteady hands or moving subjects. Depth of field is just one type of blur.
A low number (f/1.6 is fairly low. f22 is fairly high) means that only the object you focused on will be sharp and anything nearer or further away will become blurry. This is great for portaits for example as it draws attention to the person.
(f is the aperture and also affects the amount of light. You can shoot with a lower shutter speed if you have a wide aperture/low f number)
The "mm" number is the amount you're zoomed in. Wide is a low number, telephoto from a distance is a high number.
But blur can come from other things. Cheap lenses, unsteady hands or moving subjects. Depth of field is just one type of blur.