Application form
An application form is the interface used to submit information and documents for a specific job. It collects the details an organisation asks for in that application.
The form is not the application
An application form is the collection interface for one job. It can ask for contact details, a CV, a cover letter, and answers to questions related to the role. The appropriate information depends on the role, process, and purpose of the collection.
A knockout question can be one part of a form. It applies a configured disqualification criterion. The form still has a broader purpose than that one rule.
Where the boundary sits
Each required field should have a clear connection to the next decision in the process. A CV can be required or optional; a cover letter may not need to be collected at all. Those are choices for a particular role, not universal requirements.
Extra questions are useful only when their answers are needed for the selection process. Collecting information that will not be used makes it harder to explain the purpose of the form.
How to decide what to change
The form is neither a complete legal assessment nor a replacement for screening. Data necessity and retention depend on context; see GDPR in recruiting for the legal framework.
A lower completion rate does not identify the field or step that caused it. Define form starts and successful submissions, retain the same measurement conditions, and investigate the journey before attributing the change to one element.