What are follow-up sequences?
On Pro, a sequence is a follow-up cadence you define once. Enrol a lead and each next step lands on your follow-up list when it falls due.
A follow-up on its own is free and always will be: give a lead a date, and the CRM reminds you. A sequence is the template that does that for you over and over — call on day one, send listings a few days later, check in the week after — defined once and applied to any lead you enrol. Sequences are part of Pro.
When a step falls due it becomes an ordinary follow-up on your list, with the same due and overdue notifications as any other. The sequence does not send emails or messages by itself; it makes sure the next step is in front of you on the right day, so nothing depends on remembering.
Sequences put steps on your own list. Emailing quiet leads new listings automatically is nurture — see "How does nurture work?".
If an account drops below Pro, sequences already running keep raising their steps, so work you planned is not silently lost. Creating new sequences and enrolling new leads needs Pro again.