Some exchanges have fees structured like: https://www.kraken.com/help/fees.
The docs say "fees are calculated as a percentage of the trade's quote currency volume". There are two columns in the chart; I'm not sure what places me in one column or the other.
In this context, I looks like "maker" means that you place a limit order that sits on the book. If you place a market order or you place a limit order that crosses an order already on the book, you are a "taker." The "makers" are making liquidity by placing orders that are available to satisfy later market orders. The "takers" are removing liquidity by reducing the number of orders on the book that can match against any subsequent orders.
Not sure why @Brick's answer was voted down; let me try to state it more precisely.
maker
Type 1 (seller): You tell the exchange that you want to sell at price P, but P is higher than the highest price at which any Type 2 maker is currently willing to buy. (You're demanding too much money in the eyes of everyone who's said they want to buy.)
Type 2 (buyer): You tell the exchange that you want to buy at price Q, but Q is lower than the lowest price at which any Type 1 maker is currently willing to sell. (You're trying to spend too little money in the eyes of everyone who's said they want to sell.)
Congratulations! Since your request cannot be matched against any existing maker's request, you've just "made" liquidity by adding your desired transaction to the exchange's order book. Your order will sit there until it either gets filled (i.e. someone bites on your offer), expires, or you cancel it.
taker
Type 1 (seller): You tell the exchange that you want to sell at price R, and R is at or below the price currently advertised by at least one Type 2 (buyer) maker. (At least one known buyer thinks the amount of money you're asking for is reasonable.)
Type 2 (buyer): You tell the exchange that you want to buy at price S, and S is at or above the price currently advertised by at least one Type 1 (seller) maker. (At least one known seller thinks the amount of money you're willing to spend is reasonable.)
Congratulations! Since your request can be matched against some existing maker's request, it will get executed immediately (more or less) against the best available maker's price and you will have "taken" liquidity by removing one or more makers' desired transactions from the order book.
If an exchange wants to promote or penalize making or taking it can adjust its fees/rebates for each activity. And it can reduce its fees if you're a high volume customer. That's what the tables show on the web page you linked.
As you are asking specifically for Kraken, here is what I found:
What is Maker vs Taker?
A trade gets the taker fee if the trade order is matched immediately against an order already on the order book, which is removing liquidity. A trade gets the maker fee if the trade order is not matched immediately against an order already on the order book, which is adding liquidity.
Market vs. Limit orders
When you place a market order, you want to buy/sell as soon as possible, at the best available price. This is the the simplest kind of order. Market orders always get the taker fee. With a limit order, you establish your desire to buy/sell, but only at a certain or better price. A limit buy order with the limit price below market price will not be matched immediately and once it is matched the trade will get the reduced maker fee. A limit sell order with the limit price above market price will not be matched immediately and once it is matched the trade will get the reduced maker fee.
Limit sell order
Imagine you have bought 100 ETH.
Above market price: The market is currently at $150 and you think it will reach $160. You put a sell limit order at $160. We can call that order a take profit order. In such a case, you will be adding additional ETH to the book, that is why you will be paying the maker fees.
Below market price: The market is currently at $150 and you want to protect yourself against a sudden loss. You put a sell limit order at $140.
It is a mistake, because a sell limit order is "An order to a broker to sell a specified quantity of a security at or above a specified price". Because of that when you create your order, the exchange see that you want to sell at a price greater than or equal to $140. Because the price is $150, your order is executed immediately, as if you had made a market order.
In such a case, you will be paying the taker fees.
Because your order is executed immediately, you are not adding anything to the order book, and you might match another order set by someone else to buy ETH at a certain price. By matching this order, you remove the opportunity for someone else to sell his ETH at this price, thus you are removing liquidity.
You can use a similar way of thinking for the Limit buy order.
Someone is classed as a maker if they attempt to buy lower than anyone is willing to currently sell OR sell higher than anyone is willing to currently buy.
Because a maker order cannot be executed right away due to the buy/sell order book then this creates liquidity in the market, which is often favored by exchanges, hence the lower fees.
Someone is classed as a taker if their actions would in all probability be executed by the exchange immediately, in effect taking liquidity from the market. This happens when someone attempts to buy at or higher than anyone is willing to currently sell OR sell equal to or lower than anyone is willing to currently buy.
I guess you could summarise:
Maker orders are not executed immediately; buyers and sellers must reach your ask/buy before the order is executed. Taker orders are executed immediately, and take liquidity away from the market. You will be charged maker/taker fees accordingly.
First know who is maker and who is taker?
If you place an order above the current ticker price for selling or below the current ticker price for buying, you add liquidity to the market and you thus act as maker. In this case you have to pay maker fee.
If you want to fill your order at the current market price, you are taking liquidity from the market and you thus act as a taker. In this case you have to pay taker fee.
Usually taker fee will be higher than maker fee.
So Maker mean: Pending order which wait for the market price reach it sooner or later in future. While taker mean Execution of the order at current market rate.
