As mentioned above think of a Milestone as a building block to your employee experience. For example, you can build a block around employee birthdays, a block around work anniversaries, or send reminders to certain people or Slack channels regarding the former examples.
To keep it simple, a Milestone is a custom event that is sent to Slack based on the specific employee criteria you define.
A Milestone essentially has three core components—what is the purpose of the Milestone, who is the Milestone for, and where is the Milestone going. Once the Milestone has been activated (i.e. created), the Milestone will automatically fire the Slack message based on the parameters that were defined.
Milestones are not set in stone. What this means is users can update all sections of a Milestone as needed and can also activate or deactivate each Milestone too. This includes changes such as channel destinations, users included in messages, gif settings, and much more.