How long has it been since you were free of notifications on emails you haven't read yet? Maybe it's time you marked them all as read.
It's not unusual to have more than one Gmail account. Maybe you use one for business and one for your personal correspondence. Perhaps you use one for a hobby, such as couponing, or for a side gig. Whatever the reason, Gmail makes it easy to move between accounts.
Google just announced its plan to phase out Inbox by Gmail by the end of March 2019 “to focus solely on Gmail.” After its initial invitation-only release in 2014, Inbox by Gmail has been a testing ground for new email functions.