The Vietnamese word "bạn học" is a noun that means "classmate" or "fellow student." It refers to someone who studies in the same class or school as you.
You can use "bạn học" to talk about your friends in school or to refer to someone you share classes with.
In more advanced contexts, "bạn học" can be used to refer to someone you have studied with in the past, not just someone in your current class.
While "bạn học" specifically refers to classmates, "bạn" alone can mean "friend," and "học" can refer to any learning or studying context.