With the exception of Review Stages, every job stage is linked to what we call a Campaign.
A campaign is a set of pre-defined questions and messages designed to either collect information from a candidate or share information with them.
The campaign linked to a specific stage is sent to the candidate via WhatsApp or SMS when they are either created in that stage or moved into it.
When creating an application in a stage or moving an application into a stage, the linked campaign gets delivered to the candidate via WhatsApp or SMS.