Makers are typically high-frequency trading firms whose business models largely depend on specialized trading strategies designed to capture payments. Takers are usually either large investment firms looking to buy or sell big blocks of stocks or hedge funds making bets on short-term price movement.
When a limit order is placed on an exchange that is not immediately filled, the order adds liquidity to an order book for that security. Because an exchange is incentivized to attract traders and various orders to their platform, the exchange may award a maker fee lower than a taker fee to the market participant expanding the order book.
When a market order is placed, it is often executed right away. This type of order takes away part of the existing liquidity on an order book for a security. Because this is unfavorable for exchanges as the liquidity of the security has decreased, exchanges charge taker fees to deter trades from removing existing pending orders.