The deck is the main part of the skateboard that all of the other component attach to, and provides the main platform that you stand on in the normal riding position.
The materials usually consist of 7-plies of hard rock Canadian maple veneers glued and pressed together. They usually have colorful graphics painted on the bottom, and sometimes on a portion of the top as well. There will be at least one Kicktail (on Single Kick decks) and Kicktails on both the Nose and Tail (on Double Kick decks). There are 8 pre-drilled Mounting Holes for attaching Trucks with Hardware. When setting up a new deck, Griptape is stuck onto the top of the board for grip (as the name implies). Freestyle is very hard on the nose and tail so Skid Plates are also a necessity for prolonging the life of the deck.
See List of Freestyle Decks for a comprehensive list of freestyle decks.