Collateral: Any materials given directly to existing and/or potential customers that are a continuation of brand awareness, but with a stronger focus on product sales.
examples: e-newsletters, catalogs, brochures, info dvds.

You can think of collateral as being anything that you can give to a customer directly that would encourage a sale. Collateral pieces are geared to have a long shelf life, say a catalog you can use all year, or a flier that has information still pertinent three months later. The reason of this has its roots in printing. The more you print the cheaper it is per piece. But if you print a whole lot of something and then give it away slowly over time, you can not have any time sensitive promotions. The piece should be a very general look at the products and services you offer, much like an Identity piece, but with a lot more focus on selling your products and services.

Collateral pieces can also be used as a pivotal point for a sale. Your customer may be almost ready to purchase and you give them the collateral piece to send them one step closer to buying. They may be concerned about all of the functions a product offers, but their confusion is laid to rest when you give them a brochure that explains all of the products functions.