A repeatable decision framework
A stock investment strategy is a defined approach to deciding what to buy, when to buy, how much to hold, how long to hold it, and when to sell.
The rules have several parts
A strategy may define its eligible universe, entry criteria, position size, holding period, exit criteria, risk controls, and the data used to evaluate each decision.
Consistency creates something to learn from
Documented rules make it possible to review outcomes, identify where the process worked or failed, and improve the strategy without relying only on intuition.