"Hellines" is the Greek word for Greeks. It's the name the ancient Greeks used for themselves, and it's still used in modern Greek.
The word "Greek" comes from the Latin word "Graeci," which the Romans used to refer to the people of Greece.
So, to clarify:
* Hellines: The Greek word for Greeks, used by the ancient Greeks and still used in modern Greek.
* Greek: The English word used to refer to the people, language, and culture of Greece.