The best definition of a functional resume is a resume that focuses on your relevant professional skills rather than your work experience.
The largest difference between a functional resume and the more common chronological resume is that a functional resume groups your experience together under skill categories instead of job titles. Under each skill category, bullet points are used to highlight your accomplishments, whether they’re from previous jobs, school, or everyday life.
Typically, the functional resume format is used by job seekers who are changing careers or have gaps in their employment and want to draw attention toward their skills and away from their work history.