This is the 97th most frequent Japanese word.
選手
Athlete; player.
Here, '選手' is used to refer to someone who plays a sport, specifically a baseball player.
彼は野球の選手です。
He is a baseball player.
In this sentence, '選手' is used to express an aspiration to become an athlete in soccer.
サッカー選手になりたい。
I want to become a soccer player.
'選手たち' is the plural form and refers to the group of athletes participating in the Olympic Games.