"Bicycle" back design or "Custom" back design?
"Bicycle" is the name of the specific back design on playing cards manufactured by the U.S. Playing Card Co.
The design is very ornate, and features small angels riding bicycles.
"Custom" back design refers to any back design pattern that is NOT a Bicycle design.
Most playing cards that are sold in supermarkets and drugstores have a Bicycle back design.
For that reason, some magicians prefer to have their trick decks made from the same cards, so that their trick decks look identical to the ordinary decks you would buy in the store. The tricks made with custom back cards work EXACTLY the same as tricks made with Bicycle back cards.
The only difference is the design on the back of the cards.
"Air Cushion" or "standard" finish?
"Air Cushion" is a smoother finish on a slightly heavier cardstock. They have a professional feel to them.
"Standard" is perfectly functional, but just slightly lighterweight and not as slick.
"Air Cushion" will hold up better over time, and may be easier to work with overall.