A resume is the representation of your professional self. It is a concise compilation of your educational and professional experience, as well as the skills that make you desirable for the workforce. It is what you use to sell your merit and skills to potential employers.
There is not one resume format that works for everyone. There might not even be only one resume format for you and it could benefit you to have multiple formats of your resume available. For example, if you’re applying for a job and you don’t know whether your resume will be submitted through ATS, submit both a chronological resume and use a functional resume for your in person interview.