There are four ways in which a question may be set up to accept answers from the student: as a multiple-choice question, as a multiple-selection question, as a free-form short answer question, or as an image question. All but the free-form answers can be graded automatically online.
Multiple-choice items are represented by radio buttons. The student selects exactly one of these and earns full credit by selecting the one correct choice.
Multiple-select items are represented by check boxes. The student may select all, none, or some of the boxes. Each box has an associated point value (which may be negative). If you select a box you get the points associated with that box added to or subtracted from your score.
An image question is like a multiple-choice question except that the radio buttons are replaced by images (usually .bmp files), and clicking on any image causes the exam to be graded immediately. These are only useful for single question quizzes.