The DataEntry property limits the form to new records. The new records stay in the form's recordset until you close the form and they can be changed if you scroll back to them. So, if you open the form and add 10 records, those 10 records will be available until you close the form. The next time you open it, its recordset will be empty.
If you set the DataEntry property to yes and leave the other "allow" properties at yes, You can change and delete any record in the recordset of "new" records. But once you close the form, the recordset is empty until you add more new records. If you change the other "allow" properties to no, you can add new records and scroll back and forth in the recordset but you can't change or delete any of the new records.