If you are asking this question, then it means that you are pretty new to elearning: so, welcome! Scorm is the elearning industry standard format to exchange elearning content. It contains embedded html for running an interactive course. It also helps store info regarding embedded quizzes, student progress, completion status etc. It interacts with most LMS (learning management systems) and is able to provide basic level of analytics related to the students taking the course.
In summary, as opposed to a video, or a static powerpoint, Scorm provides for the interactivity (similar to a flash file), and also provides reporting capabilities to the LMS.