Your resume is arguable the single most important part of the application process. A well-organized, relevant resume will set you up to get an interview, while a poor resume will get completely lost in the sea of applicants. This is a fairly modern concern, as job postings now get thousands of online applications a day.
Some companies will indicate that they want you to submit a CV rather than a resume. A CV and a resume are not the same. CV stands for “curriculum vitae” and is meant to be an expansion of your resume. It is much longer than a resume, often three pages or more, and focuses mainly on your academic and professional accomplishments, with a particular focus on education.