Maker is the counterparty of the trade where the order is not executed immediately. It provides liquidity for other traders.
Taker is the opposite of Maker, which means it is the counterparty of trade whose order is filled immediately. Taker orders never sit on the order book.
What's the significance?
Maker, in most cases, has a smaller or negative fee, meaning the trader receives a rebate after the order fills.
Taker means the trader is taking liquidity and paying a larger transaction fee.