What is the difference between the feast of Passover and feast of unleavened bread?

Nowadays they are identical and coterminous. But in Biblical days, Chag haPesach/the Passover festival, was the first afternoon/evening of the holiday, terminating with the eating of the pascal lamb sacrifice along with matza/unleavened bread and marror/bitter herbs, and the recitation of certain Psalms and other passages from The Bible and rabbinic texts. Chag haMatzot/The Festival of Unleavened Bread then lasted for the next 7 days, after which leavened products could once again be eaten.