As a buyer or a seller, you have 2 possibilities to determine if you become a maker or a taker of the transaction:
Maker - If you place an order that gets added in the open order book and is pending to be matched, you are the maker. Maker creates liquidity by placing new orders. The order will be in the book until completion or unless canceled.
Taker - If you place an order that gets matched against an order already in the book, you are the taker. Since taker’s request will be matched against a maker's current request, it will get executed immediately. Taker removes liquidity by reducing the number of orders in open order book.