A resume is a marketing tool - an outline of your experience and abilities. It is used to apply for jobs and to present yourself to possible employers. The information in a resume is only part of the story. How your resume looks is also an important part of the impression you will make on an employer. Employers use resumes to evaluate job applicants.
Employers receive many resumes and are usually in a hurry.
They won't waste time on resumes that are hard to read, sloppy or incomplete. A resume can help you complete applications for employment. Resumes are not always asked for by employers. However, providing a resume makes a good impression on employers. It also gives them something to refer to if they want to contact you later.