With just little variations in connotation, all of the words are extremely similar:
A person who has successfully completed the hiring process and begun working for a company, or who is actively looking for work.
A candidate is a person who has applied for a job but has not been hired yet. To get a job, candidates must go through the selection process.
A worker is any individual who performs labor or renders services, irrespective of their job position; this includes temporary workers, independent contractors, self-employed people, and employees.
An official is a person who handles office or administrative tasks, frequently in institutions or the public sector. An employee is a person who performs services for an employer under the terms of an employment contract in return for payment. All of the previously listed categories are included in this word.
Hiring is the process of finding, attracting, selecting, and onboarding new employees to fill open positions within an organization