An active client is a client you are currently coaching (for example: they are submitting check-ins, have an active program, or are messaging with you). You can have unlimited coaches and staff on every plan.
The "Enterprise" Pono package places no limits whatsoever on how many clients you can have. The other packages have a client limit — for example 50 active clients, or 250 active clients.
You can archive clients and still let them sign in on your website and mobile app to see their previous data, but as long as they are not active they will not be able to do anything — send you messages, log workouts, submit check-ins.