This option allows you to create a record in the chosen table through a portal. When this option is checked, you get a blank row at the bottom of the portal in which you can set data. When you put something in a field, it automatically fills in the foreign key (the related key) with the primary key (the parent key - the Table occurrence upon which the layout is on)
If you have a "Students" table and a "Contacts" table, and they are related in this way: STUDENTS::ID = Contacts::ID_Student, and the "Allow" option is checked under the Contacts table, then you can create a new contact within a portal on the students layout.
The last row, the one with the trash can on it is the place I can make a new record.
Does this only work via a portal? Is there any other way it can do the creation for you? Thanks
No, it does not require a portal. You can place a field from the related table directly on the layout without using a portal and entering data into that field creates a related record if no related record exists.
The MagicKey method for working with related data also exploits this option in a way that can enable creating multiple related records without using a portal.