In the UK the two words mean the same thing. In the US they do not: a resume is a short, tailored one-to-two page summary, while a CV is a long academic document listing publications, research and teaching.
What you send depends on the country and the field, not on the word used in the advert.
Beyond length, the differences are about what belongs on the page.
Both are read by applicant tracking systems before a human sees them, so both need clear section headings, standard fonts, real dates and the wording used in the job ad.
Both are also judged on evidence. Whichever word the employer uses, replace duty descriptions with what you actually changed — a number, a scale, an outcome.
In the UK, Ireland and much of Europe, yes — 'CV' is the everyday word for the two-page document you send with a job application. In the US they differ: a resume is a short targeted summary, while a CV is a long academic record.
Send a resume — one to two pages, tailored to the posting — unless the role is academic, scientific or medical, where a full CV with publications is expected.
Not in the UK, US or Ireland; leave it off. Some European countries such as Germany still commonly include one. Follow the convention of the country you are applying in.
Draft your CV, run the ATS check against a real job ad, and download a PDF.