Is BNB and smart chain the same?

Could you please clarify for me if BNB and Smart Chain are interchangeable terms, or do they refer to distinct concepts within the cryptocurrency and blockchain realm? I've been hearing both mentioned frequently but am somewhat confused as to whether they refer to the same thing or have separate functionalities and applications. Could you elaborate on the differences, if any, and how they are related, if at all? Your explanation would greatly assist me in understanding this aspect of the crypto world.