After connecting your accounts, the app will automatically create video flyovers of your route, like my example below that I posted to Instagram. On my first try, the video was not available for at least 30 minutes after I synced with Strava.
If your photos are geo-tagged, and uploaded to Strava within 15 mins, Relive will embed them in your video as well. It will show them at the exact point on the route that they were taken. Very impressive.