This is a summary of the latest card changes to Rotation. See here for older card changes.
Rotation is one of two constructed formats in Shadowverse (the other being Unlimited).
A Rotation Deck consists of 40 cards chosen from the Basic Set + the latest 5 sets released (shown above).
A new expansion set is released approximately every 3 months, at which time the oldest set in rotation rotates out. There are 4 expansion releases in a calendar year.