Whether a field 'is required' or not is up to the Process mapper. By making a field required, when the Task is eventually run by a user, the Task can't be completed until the required section has been seen to.
How to complete that required field will depend on what sort of field it is. A file upload field will need a file uploaded, a text input field will need text to be entered, and so on.
The 'is required' option is not selected by default so remember to double check if you need any particular field to be completed as you're adding them to the User Task.