There may be several reasons why your iPhone is performing slowly, such as too many resource-hungry apps or not enough storage space. If you want to return your iPhone to its factory default settings, you can use your PC and iTunes to format it. Formatting is also prudent if you bought a used iPhone; this procedure removes the previous user’s data and customized settings, restoring the device to factory-new condition. Tips Writer Bio

How to Format an iPhone From a PC - 43