Correct me if I'm wrong, but B.C. and B.C.E. end at exactly the same time. How can one be less defined than the other? You also haven't revealed who taught you this. You must also be one of the conspirators.
They're merely my assumptions. I've been aware of AD and BC for as long as I can remember as well CE and BCE for just as long. Both were used by students in college and teachers in high school.
One is simiple religious significance and the other is used by nations like China who do not use a calendar based off the Christ's ambigous date of birth.
P.S. I prefer BCE and CE as a matter of rule.