A send is one dispatch of one article to a newsletter's list: when it started, when it finished, and the three numbers it finished on. Not to be confused with Senders, one heading below: a sender is the address an article goes out from and is configuration, a send is something that happened.
Starting one is an operation under Articles, because it is a moment in an article's life. Reading what became of it is here, because a run is its own object with its own identifier and one article can have more than one.
The same run is announced as a send.completed event, carrying the same
three numbers under the same names, and these operations are how a
consumer reads them back afterwards from the identifier that event
carried. Needs sending.