Do public registrants count as 'Users' on the account

Do public registrants count as 'Users' on the account

Hi, this may seem dumb to ask but, whilst at max our organisation will require 5 users to administer the apps and databse, we wish members of the public to be able to register, log in, add and edit their information on our database via a web form. Will those people count as users on our user count, or simply as public data access through our web form? We are hoping for thousands of registrations but if they count as 'Users' it would be financially unviable.