Revival Tryouts are a type of Tryout that rerun past Limited Time Tryouts. Revival Tryouts will be limited to around 3 days. Not all past Tryouts will be rerun, however Revival Tryouts will generally follow a chronological order of previous ones, starting with the oldest. They are spontaneous and do not come at any fixed interval.
The rates for getting the limited-time SSR or SR card will be boosted.
Tryouts are NOT to be confused with Revival Token Tryouts. Despite their similar names, the two are very different. Revival Tryouts use Gems and their Cards are exactly the same as the original tryout that is being revived. The only difference is what time Revival Tryouts are held at.
Revival Tryouts are also NOT related with Revival Events. Again, these Tryouts are only a chance to get cards you have missed out on.