This feature allows you to create a vibration alert on iPhone. These alerts can then be set as notification or any incoming calls to incoming calls. The advantage of custom vibration is that, without hearing the ringtone, only by experiencing the vibration, you can understand from which number the phone is coming or what's the notification. To create custom vibration, open the following options on iPhone: Settings> Sound> Ringtone> Vibration> Creative New Vibration
Now record the type of vibration by touching on the screen. For example, if you touch the screen two times in a row, then the vibration alert will vibrate twice in a row. In this way save your custom vibration.
If you want to set custom vibration for any contact, go to the contact option of the contact and select the custom vibration in place of the ringtone.