What do Taker and Maker mean?

Taker：

When you place an order that is partially or fully filled before it is included in the order list, this type of transaction becomes a Taker.

Transactions on Market Orders are Takers because Market Orders are never included in the Order List. These trades all take volume from the order list and therefore become Takers.

Maker：

When you place an order, such as a limit order, which is partially or fully incorporated into the order list, any subsequent trades from that order are Makers.

These orders add volume to the order list and contribute to "market making" and are therefore referred to as a Maker for any subsequent trades.