Backup

About backups in iCloud and iTunes - Apple Support

yes, however your contacts you should be syncing with a cloud system or email manager.

saboum wrote:

If i back up my iPhone to my computer, reset it to factory settings, and then restore it, all my photos, videos, music, contacts will be back?

Understand that iTunes content is not contained in your backup. That is assumed to be in your iTunes library, so you would need to do this restore from the computer that contains your iTunes library. Otherwise, your music and apps could be lost. Photos and videos in the camera roll are in the backup, not those synced from the computer. Again, the videos are supposed to be in your iTunes library. Your camera roll is in the backup, but for safe keeping, I would import the content to the computer for backup, incase there is a problem with the backup. Contacts are in the backup, but they should be synced to a supported application on the computer or to a cloud service to ensure their safety as well. Expecting the backup not to fail or safely keep all of your content in that single place is not a good way to do things.