When you place an order that does not fill immediately, you are a "maker".
You are "making the market" by creating an offer that someone else may take.
When you place an order that fills immediately, you are a "taker".
You are "taking" the price that you want from the existing orders in the order books.
Adara charges a lower trade fee for makers than takers.
This creates an incentive for users to place orders on the books and add liquidity to the market.