Refers to a person who has applied for a position, school, or program. Often used in formal contexts such as job applications or university admissions.
The number of applicants to this university is increasing every year.
Applicants should submit their résumés.
候補者 means 'candidate' in the sense of a nominee or someone being considered, often in elections or selections, whereas 志望者 is specifically someone who has applied.
Compound of 志望 (しぼう, 'aspiration, desire to apply') + 者 (しゃ, 'person').