Here’s a simple answer: any information that will convince an employer that she should take the time to interview you.
A client recently sent me a resume to evaluate. He’s had 4 jobs since graduating from college. For each job he lists 2-3 bullet points with generic information about his duties. When I told him that this format was not selling his abilities, he told me that employers don’t want to read “a lot of words.” My answer was to show him several job postings, all of which stated specific skills and attributes. Employers want evidence that you can do the job. They also need to seem some record of achievement or success stories.
Test your resume by looking at each element and asking this question: Why does an employer want to see this?