Two teams, the Tomcats and the Huskies, battled for the city championship.
An appositive phrase renames the noun that comes directly before it. It is also surrounded by commas since the phrase can be removed from the sentence without altering the grammatical structure. In this sentence, the Tomcats and the Huskies rename, or clarify, which two teams are being talked about. Appositive phrases are frequently used to clarify who or what something is. For example, my sister, Sarah, is happy. The appositive "Sarah" clarifies the name of the sister.