Maker fees are paid when you add liquidity to our order book by placing a limit order below the ticker price for buy, and above the ticker price for sell.
Taker fees are paid when you remove liquidity from our order book by placing any order that is executed against an order on the order book.
Maker and taker fees depends whether you are increasing or decreasing the size of the order book. A maker is the one who provides liquidity to the market. In other words, maker is the one who places limit orders on the order books. Without limit orders sitting on the books, the price of coins would fluctuate as the exchange tried to match buy market orders and sell market orders. On the flip side, “takers” take liquidity. That is, they place market orders to immediately buy/sell orders sitting on the books.
If you buy or sell using a market order, you will pay the taker fee because a market order immediately removes liquidity from the order book.
If you place a limit buy below the current market price, or a limit sell above the current market price, then you will pay the maker fee if the market moves into your limit order because you added liquidity to the order book, while other traders took your offer from the order book.
For clarification please take a look at the below example.
Assume Bob sells 1 BTC at $2000 and Charles sells 1 BTC at $1995. If you add a buy order at $2000 for 2 BTC, you will be match the offers of Bob and Charles. You're a taker. If you add a buy order at $1900 for 2 BTC, your order won't be matched and you're a maker.