Keyword-overlap score
Read this before acting on the score. Keyword matching is a heuristic. Real applicant tracking systems vary widely in how they parse and rank resumes, and this score is not an ATS pass/fail prediction or any kind of guarantee. Stuffing keywords you cannot back up is counterproductive: it gets you interviews you will fail. Only add a missing term if it truthfully describes work you have actually done.
Matched keywords (in both)
Terms and phrases from the job description that also appear in your resume. Count = times mentioned in the job description.
Missing keywords (in the job description, not your resume)
Ranked by how often the job description repeats them, since repeated terms usually matter more. Terms flagged requirements appear in lines that look like hard requirements (lines containing "required", "must", "you have", "qualifications"). Review those first, and only add ones that are honestly true of you.