The "Users" tab lists all the teachers, staff, and users who have access to your school in Schoolrunner. If you have multiple schools, this tab will also list any superusers who have access to multiple schools, even if they're based at another campus.
You can manage users individually or in bulk, via a spreadsheet upload. You can also send individuals emails that let them reset their password, if they're having trouble logging in (find this in the gear menu).
Users who have their accounts created individually in the website will receive an automated welcome email, explaining how they can set up their password and log in to Schoolrunner. Users that are created via the spreadsheet upload do not receive this welcome email.
See the next tab, "User Groups & Permissions", if you want to determine which areas of Schoolrunner individuals can access.