A taker fee is a type of a transaction fee charged when a participant places an order that is directly fulfilled. This means that the placed order is matched with an already existing order in the market. Logically this allows a participant to take away the liquidity. This is why such a transaction costs a fee called the “Taker Fee”.
Michael has already placed a sell order of 1 BTC for $1000. Duke is another participant who then places a buy order of 1 BTC for $1000. As there is already a sell order of 1 BTC for $1000 put in by Michael, Duke’s order will be matched instantly and a “Taker fee” will be charged to Duke.