A Merge Field is a field that you input into a piece of text from your admin interface and that auto-fills value automatically when a primary stakeholder submits an application.
Eg. you created a Process description (or welcome message) that says “Hi {CONTACT_FIRSTNAME}”. The merge field here would be used to automatically pull the first name of the client detailed on the contact card.
You can use merge fields in your custom emails, portal description (welcome message), in e-contracts, or even in HTLM forms.
Merge Fields listed by category according to your needs: