The applicant is the person or company who will be applying to register/incorporate/create/form the company.
The Applicant must confirm the truth of the details of the application and various other matters.
If you are helping a person or company other than yourself to form the company, then Incorporator suggests that the other person should be the Applicant.
If you are forming the company for yourself, then Incorporator suggests that you should be the Applicant.
The applicant may, but need not be, one of the proposed director(s), secretrary(s) or member(s)/shareholder(s).