Market Taker

A market taker is a trader that places orders which immediately get fulfilled. A user who places a market order is a taker because their order is immediately fulfilled and removes liquidity from the market.

If you're okay with the current price when buying or selling and place an order to trade at that price, you're a market taker. You literally "take" volume from the market.

Market Maker

When you place an order at a price different from the current market price, you are a market maker. Maker trades are partially or fully placed on the orderbook and aren't (fully) executed at the moment of placement.

A market maker will place buy orders at lower prices and sell orders at higher prices. Limit orders, stop orders, and OCOs are market maker orders. If you place one of these orders, you're helping to "make" the market by adding liquidity.