When you place an order that goes on the order book partially or fully, such as a limit order, any subsequent trades coming from that order will be as a “maker.”
These orders add volume to the order book, helping to "make the market," and are therefore termed the "maker" for any subsequent trades.
When you place an order that trades immediately, by filling partially or fully, those trades will be "taker" trades before going on the order book.
Trades from Market orders are always Takers, as Market orders can never go on the order book. These trades are "taking" volume off the order book, therefore called the "taker."