My current bill contained a line that states BACK TAXES on it. What does this mean?

According to our records, there are past due taxes in your name, or on the parcel of property in question. Please call the office with more detailed questions 860.489.2209 x6. Delinquent taxes and interest must be paid in full on a specific property before payment on current bills can be accepted. Any payment you send in toward your current taxes will be applied to the back taxes. (CGS 12-144b).