This is the 300th most frequent Russian word.
сам
"Sam" means "self," "oneself," or "on one's own."
Here, сам emphasizes that the subject of the sentence performed the action independently, highlighting autonomy.
Он сам сделал домашнее задание.
He did the homework himself.
In this context, сам indicates the decision-making being done personally by the addressed individual.
Ты сам выбери, что тебе нравится.
You choose yourself what you like.
Here, сам is used to emphasize that the speaker witnessed the action directly and in person.