The recovery of the iPhone is a process as a result of which your phone will return to its "native" (factory) settings, and its iOS will be updated to the latest version. The recovery procedure is necessary through iTunes (ideally - the latest version) as follows.
Let's start with the fact that you immediately check the "Find iPhone" function. If it is enabled, through the ICloud settings we do inactive, that is, we turn off. To speed up the recovery process and avoid unnecessary situations, we find and download the necessary version of iOS to the computer. Please note that when restoring your iPhone will be "demolished" all photos, video, music and personal information (contacts, calendar). Therefore, if this content is very expensive to you, make it backup (on the same computer and in icloud).
You can synchronize your iPhone to completely give "in hand" iTunes, without downloading the desired firmware yourself. In this case, the options for selecting the IOS version will not have - iTunes will install the latest firmware version to your device.