|An appositional word or phrase introduced by or is set off by commas:
He brandished his khanjar, or dagger, as he spoke.
When or introduces the final member of a series of three or more, it is preceded by a comma:
coffee, tea, or milk
After a compound subject or a series connected with or, the verb agrees with the final member:
wine or cocktails are served
soft drinks, cocktails, or wine is served