This is the 1220th most frequent Russian word.
лето
Summer.
In this sentence, "лето" is used as a noun denoting the season of summer.
Я люблю лето за его теплую погоду.
I love summer for its warm weather.
Here, "лето" is employed to refer to a recurring time period, specifically the summer season.
Каждое лето мы ездим к морю.
Every summer, we go to the sea.
In this case, "лет" is used as the plural genitive form of "год" (year) to indicate a span of years.