Position
Basics
What it means
An open trade you currently hold. A long position means you own the asset; a short position means you owe it. Closing the position ends the trade.
Example
If you buy 200 shares of MSFT and have not sold them, you hold an open long position of 200 shares. Selling all 200 closes the position to zero.
Mistake beginners make
Beginners open too many positions at once and lose track of total exposure. Five "small" long positions in tech stocks are really one giant bet on tech.