Execution
Basics
What it means
The whole process of getting your order filled: routing it, matching it, and reporting the trade back to you. Good execution means fast fills at fair prices.
Example
A marketable limit order to buy 500 SPY shares might execute in under 100 milliseconds across several exchanges, filling 300 at $450.01 and 200 at $450.02.
Mistake beginners make
Beginners blame "the broker" for bad execution when the real cause is using market orders in illiquid names. Order type, not the broker, usually decides fill quality.