This is the 101st most frequent Russian word.
стал
"Stal" means "became" (past tense of "to become").
Here, 'стал' is used as a past tense of 'становиться', indicating that someone took on a new role (became).
После окончания школы он стал врачом.
After finishing school, he became a doctor.
In this sentence, 'стал' is used to indicate the beginning of an action, often followed by an infinitive.
Старый дом стал рушиться от сильного ветра.
The old house began to collapse due to the strong wind.
Here, 'стал' could be interpreted in a figurative or metaphorical sense, suggesting progress toward a goal.