From Bulbapedia, the community-driven Pokémon encyclopedia.
Pikachu receiving a Nice Card
Nice Cards are collectible cards obtainable in the Pokémon Channel video game. There are three types of Nice Cards: Single cards, which have a Pokémon's picture on them, Motion cards, which have a hologram of the Pokémon, and Platinum cards, which have a hologram and play the Pokémon's cry. Most Pokémon are available in all three, but only one is needed for it to count towards a player's total cards. Nice Cards can be obtained by the player by receiving them from Pokémon met in the game, or they can order them in booster packs from the Shop 'N Squirtle channel. There are 110 different Nice Cards in total, nine of which are special Pikachu cards.
Nice Cards are kept in the player's Binder. The Binder must be ordered from the Shop 'N Squirtle channel. After the player has collected 25 cards, Professor Oak will reward the player by upgrading their Binder into the Superior Binder. When the player collects 50 cards, they will receive the Prime Binder. As a reward for getting all 101 of the main set of Nice Cards, Pikachu will give the player a set of nine Pikachu Nice Cards that come in three different varieties, making the total number of cards to be 110.