An expungement is a specific legal procedure with a specific meaning, and you generally need to hire an attorney to get one done. It sounds more like you entered into a deferred prosecution agreement (DPA), which is a typical outcome for a lot of minor in possession cases and things like that. A DPA just means that the prosecuting attorney won't pursue the case, so it won't go to court, you won't have to worry about ending up with a conviction on your record, and there won't be any record of the charge with the court or on CaseNet as long as you hold up your end of the bargain. However, your arrest records still exist and, unless you pursue an actual expungement, they will remain on file and show up on any background check that goes through a law enforcement agency.