To add to cool's good info, you sound confused about those two designations. The reason you've found both as being applicable is that they ARE both applicable. Bel Air is a model designation.
They had three models; Bel Air, 210 &150. The BA was top of the line, 210 middle, 150 base, as far as standard features and trim. Sports coupe is a body style designation, along with sedan, convertible, station wagon, etc.

As a 210 yours would have similar side trim to the BA, but without the shiney insert on the tail fins. That's the most visible que, there are other slight trim differences and upholstery is different.