This is the 7459th most frequent Japanese word.
健太
"健太" is a Japanese male given name meaning "healthy" (健) and "plump/robust" or "great" (太).
The word 健太 represents a proper noun, specifically a person's name, used as the subject of the sentence.
健太は学校へ行きました。
Kenta went to school.
The word 健太 indicates possession in this sentence, showing that the room belongs to Kenta.
すごい、健太の部屋はとてもきれいですね。
Wow, Kenta's room is very clean.
The word 健太 is used as part of a phrase indicating accompaniment, highlighting that Kenta is involved in the action.