View and Collect
Access to a form comes in two kinds, granted separately on the form’s settings.
Collect
Can fill the form in and submit records, and reads their own records. This is the grant field crews need.
View
Can read every record on that form, including records other people submitted. View never writes: it does not allow filling the form in, does not make somebody eligible to be assigned a record or chosen in a Send to field, and does not permit editing.
View is wider than it sounds. Collect lets somebody submit records. View lets somebody read everybody’s. Granting View to a large group is the change most likely to expose more data than intended — it is the wide one, even though it is the read-only one.
Both
Somebody who both collects and reviews a form needs both grants. Managers and admins have both on every form without being granted them.
Subform entries are the exception
Somebody filling in a parent form can add entries to a subform even without a Collect grant on the child form. A subform entry is part of the record they are already permitted to create, and requiring a separate grant would break every parent form the moment a child form was added to it.
Granting
Open the form, choose Settings, and under Access add people or user groups to Collect or View. A form with nobody granted is open to the whole organisation.