Rifts are dimensional oddities found all around Hotel Hideaway. You can extract coins and diamonds from them. By watching two in-game ads a day while extracting currency from a rift, you receive 15 minutes worth of currency instantly.
If you choose to watch two in-game ads after you’ve extracted currency from the rift, these videos will double the amount of currency you extracted! Different rifts contain different types of currency - the ones that contain diamonds are much rarer.
You can use them by yourself, but the more people you have working together in a rift party, the more currency you will earn! Higher rank friendships will help you to earn even more currency. One person doing a rift with you that is a rank five friend will help you more than five rank one friends.