Where the line between applicant and candidate falls varies between organisations. Some treat everyone who passes an initial check as a candidate; others reserve the word for people at interview stage or beyond. Candidates can also be sourced, meaning a recruiter approached them before they applied. In most tracking systems a candidate record follows the person across roles, keeping their full history in one place.
Shared definitions keep reporting meaningful, since metrics such as interview-to-offer ratio depend on who is counted. How candidates are treated also matters beyond the current vacancy: people who are not hired may apply again, refer friends or buy from the business. Regular updates, honest timescales and feedback where possible are signs of a well-run process, whatever the volume.