...
If the system does not have the next smallest device being targeted, it will open the main form size, and the user will need to scroll horizontally to see the entire form if the form was built wider than the screen of the device it's being viewed on. Read more below about the main form.
Language Targeting
Language-specific devices can also be targeted, whereby the form will open based on the user's device-level language settings. For example, If a French user has their device settings in the French language, and the study they are doing data entry on has a form targeted to French, the user will see that version of the form. Any data variable queries will also be presented in the device language, but the query text itself in the queries report will be stored in English.
PDF Targeting
Lastly, the device type "PDF" can be used to create paper versions of the electronic forms. This version will never be displayed to end-users. Instead, it's specifically a tool for form builders to create paper CRFs for printing.
...
How to Create Targeted Forms from the Device Dictionary
Now you have a list of targeted device sizes that can be used on any study within the hosting account.
...