You can specify the recipients when configuring a message. This determines who the message will be sent to whenever it is triggered.
Each recipient will receive their own unique copy of the message. The automatic variables will be re-parsed for each individual recipient.
A collection of recipients can be generated in several ways...
# All users
The message will be sent to all Users in the system.
# All admins
The message will be sent to all Admins of the system.
# All users in selected group(s)
Select which user group(s) should receive the message.
# Custom selection
The mechanism for setting custom recipients may change prior to the 1.0 release.
If all else fails, you can generate a custom list of recipients via Twig. Use the Twig snippet to build an array of either Users or email addresses.