All items inherit, by default, from the Sitecore provided "Standard template". As a developer you may change security settings on particular fields on the Standard template, thereby granting or denying roles or user Read or Write access to Standard template fields.
Note that most of the Standard template fields are Denied access to the Everyone user. This means that only Administrator users may see these fields. If you want to make currently protected fields visible to non-Administrator users, you must first set the Read access right to Inherit for the Everyone user. Therefore, set the Read access right to Allow for roles and/or users that you want to be able to view the given field. Allow Write access for roles and users that should be able to modify the fields.