The "Maker" is someone who places an order, and it does not trade immediately, so your order stays in the order book and waits for someone else to fill/match with it later, which means you are providing liquidity to the order book.
The "Taker" is someone who decides to take liquidity from the order book by placing an order that is instantly matched with an existing maker order on the order book.
It is important to differentiate between ‘maker’ and ‘taker’ as many exchanges operate on a maker-taker fee structure, providing different trading fees to makers and takers.
For instance, the trading fees of perpetual contracts on BIT i.e. 0.04% for maker & 0.06% for taker.
Maker fees are generally lower than taker fees. That’s because a “maker” provides liquidity to the order book (by placing an order that may be matched in the future, this “makes” the market, just like place an inventory on the store shelf) whereas, a “taker” consumes the book liquidity by ‘taking’ an order from the order book (taking away inventory from the store shelf).
Trading fees are determined once the trade executes. The moment your order fills, you will then pay either the maker or taker fee depending on whether you were the maker or the taker of that trade.
When a trader places an order to long or short a contract, there are typically two order types: market order and limit order. Market orders are transactions meant to execute as quickly as possible at the current market price. Conversely, a limit order sets the maximum or minimum price at which you are willing to buy or sell, transactions are to be executed at the limited price or within the limited price range. Therefore, when you place a limit order, the price entered actually represents a price range.
It is sure that all investors that place market orders are Takers, and it’s impossible to convert the role.
For a limit order, when it enters the matching process and cannot be filled immediately with an existing order, then it will enter the order book and wait to be executed in the future, in such case, the trader becomes a Maker on the order book.
When a limit order is placed, if there is no matching order in the order book, the trader will be marked as a Maker; However, if there is a matching order at the time when the trader places a limit order, and the transaction is executed, then the trader now becomes a Taker.
Therefore, when a user places a limit order, it does not mean that you are necessarily the Maker, the final status is determined upon the trade execution.
Conclusions:
Maker
Limit order, but is not immediately filled with the matching order, and enters the order book.
Taker
1) Market order; or
2) Limit order, and is immediately filled with the matching order in the market.
The Scenario when Maker Changes into Taker: When the order is placed, there is no matching order in the order book. At this moment, the trader is a Maker, but when a matching order instantaneously appears and the transaction is executed. At this point, the order is converted from Maker to Taker.