Maker and taker
What is the difference between placing an order that waits and one that trades immediately, and why does it matter for cost and execution?
In plain words
A maker order rests on the order book at a chosen price, adding liquidity, and may sit unfilled until someone trades against it. A taker order executes at once against the best available resting order, removing liquidity. Exchanges usually charge takers more and sometimes rebate makers.
Why it matters
The role decides both the price you get and the fee you pay. Makers choose a level but risk never filling during quiet markets; takers guarantee a fill but pay the spread and the higher fee, which matters most in fast moves.
In a real week: ETH, week of 30 April 2018
ETH's dollar volume that week was 0.77bn, or 1.53 times its prior 12-week average, inside a 33.85% range. The largest one-hour move was -5.64% at 00:00 UTC on Tue 2018-05-01, and the week's low of 627.58 came at 01:00 UTC the same day, before the high of 839.99 on Sun 06 May at 02:00 UTC. Volume of that size alongside one-hour moves of that size is the setting in which the maker-taker choice is weighed.
A common mistake
Assuming maker orders are simply better because of the lower fee. A maker order can remain unfilled while the market moves away, turning a saved fee into a missed trade.