Android SMS read vs seen column?

Wh开发者_如何学编程en getting the column names of content://sms there are two that appear to be the same column? One is named "read" and one is named "seen" does anyone know the difference(s) between them?

As best I can tell from the source code, "read" means that the user actually entered the SMS application and has read the message, and "seen" means that they have been notified about it in the tray.