The attendance icon takes you to a student's attendance sheet from any card except the seating chart. While in the seating chart card, the same button will produce a prompt asking you for the student's name and will then take you to his or her attendance card.
The grades button performs the analogous task as the button icon.
If you have selected (hilited) an assignment on a student's grade card, then this button will take you to that assignment description in the "Lesson Plan" stack.
Self-explanatory. It takes you to the first card of your stack, which is always the seating chart.