After you submit your trademark application, it will be examined by a USPTO Examining Attorney to determine whether it satisfies the criteria for registration. If it is approved, it will be published for a period of thirty (30) days for "Opposition." An Opposition is a legal proceeding at the Trademark Trial and Appeals Board that can be initiated by anyone who believes that allowing registration of your mark will cause them some harm. For instance, if your application to register KOKA-KOLA was somehow approved for publication, you could anticipate that the Coca-Cola Company would file an Opposition.
Under some circumstances, a party may get an extension of the time to file an Opposition. Status Code 773 is triggered after such an extension has been granted. It indicates that the extended Opposition period has been terminated. No further action is required on your part at this time. For more information, see the notice you received from the USPTO. For more information on the Trademark Application Process in general, visit: