This is a really good magic card trick where a card is seen to change into another card after it has been given a magic rub. This illusion is performed right under your audience's nose which makes it even more convincing. Such is the beauty of close up magic.
The How To Magic Instruction Video on this page shows the card trick being demonstrated then gives an explanation of how the magic trick was done.

Method : Make sure that the card that you wish to change to is directly under the top card. When you place your hand on top of the cards, gently push the top card up a little. This will expose a little of the second from top card. Now use the fleshy part of your palm ( the part nearest the wrist ) to pull back the second card until it clicks free from the pack.

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Now push forward and this card should slide over the pack to become the new top card. This move will be hidden from view from your audience who should be viewing the move from above, looking down on the back of your hand.