This is the 2447th most frequent Japanese word.
上田
"上田" is a Japanese surname meaning "upper rice field."
In this sentence, "上田" is used as part of a proper noun to refer to a person, Mr. Ueda.
上田さんは本屋で働いています。
Mr. Ueda works at a bookstore.
Here, "上田" is used as a geographical name, referring to Ueda city.
上田市は山に囲まれています。
Ueda city is surrounded by mountains.
In this sentence, "上田" is again used as a proper noun to represent a place, specifically Ueda city.