The overview report lists all the courses a student is enrolled in together with the total grade for each course.
Students can access their overview report from within any course by following the grades link in the course administration block, then selecting "Overview report" from the "Choose an action" dropdown menu at the top left of the page.
The overview report is not relevant for teachers or non-editing teachers. For new Moodle 1.9.5 installs the view overview report capability is not set for the default teacher and non-editing teacher roles. For administrators upgrading to Moodle 1.9.5, Simplifying the gradebook by changing permissions provides details of how to make this change for teachers and non-editing teachers.