I you only have one camera on the rear of your phone chances are it’s not optical. That being the case your only zoom option is digital zoom. Digital zoom using the software basically to pre-crop and image. Think have you ever taken an image then crop it later only to find that it lowers the quality? That’s how digital zoom works. Although it has been improved with newer phones through camera improvement and software upgrades, it’s nothing compared to optical zoom. Digital zoom can also be found on many low level and cheeper point and shoot cameras. It’s smart just not to use the zoom if you have a digital zoom lens because you can always crop the image later.