Two types of missions you will see inside of The Show Diamond Dynasty are Collection and Exchange missions. Although they sound similar, there's a few important differences to be aware of.
Collections: Collecting a card will lock the card into your inventory. You will still be able to use the item during gameplay, but you will no longer be able to sell the item in the marketplace.
Exchanges: Exchanging a card will remove the card from your inventory for points towards a mission or reward. You will no longer have access to use or sell the item.
These missions often earn you points and/or are required in different programs, but any decision you make on a card is permanent and cannot be reversed.