How to Perform the "underpants" card trick

this video is about doing a card. The first thing you do is show a card to a person but you don't see it. Then you place that card face down on the table. Then you go through the deck of cards and take out four small decks of cards and place them face down on the table. Then put there card aside in the middle of the deck of cards. Then you take a card from the top of the deck and place it face up on the table. Now place the four deck of cards together in your hand and spread them out on the table. The cards will be facing up and will reveal the card the person saw.