Hi Ted, here is the summary from the high level perspective.
1) SMS can be send from long number to long number, it goes via external SMS provider and can be used to communicate with non-RingCentral users or users from a different RingCentral account
2) Pager message can be sent only between users of the same RingCentral account idendified by their short numbers.
3) SMS can be sent only one-to-one: if you need multiple recipients you should send multiple messages with the same subject.
4) Pager messages allows to indicate multiple extension numbers as recipients, so the message will be delivered to a group of people
5) Pager messages can be sent to Call Queue extension number. In this case it will be forwarded to all current members of this call queue.
6) SMS is currently supported only for US and Canada accounts. Pager messages supported in UK as well.
