The difference between names of Harappan Civilization and Indus Valley Civilization

Both the names are coterminous. Harappa is an archaeological site in Punjab, Pakistan and this was the first site where the remains of the civilization were first found. That is why it is called Harappan Civilization.

Since it started in the river valley of the Indus River and largest concentration of the settlements has been found along the course of this river, it was called Indus Valley Civilization.