The ARROW keys

LEFT and RIGHT for horizontal scrollbars, and UP and DOWN for vertical ones;

Each key changes position by the line (or singly). If the SHIFT key is pressed, it scans by the pagesize. On the other hand, if the CTRL key is pressed, it moves either to the absolute begining line or the farthest possible line reachable considering the indent.

These operations are similar to mousewheel-keyboard combinations.

The PGUP and PGDN keys

The key changes the position of the scrollbar by pagesize. If the SHIFT key is pressed, it scans by the current fine extent. On the other hand, if the CTRL key is pressed, it moves by the current coarse extent.

The HOME and END keys

The keys move either to the absolute begining line or the farthest possible line reachable considering the indent.

For both SHIFT and CTRL modification, consider the whole range of the scrollbars as divided into several segments or sets of lines. These segments are equal to either the fine extent (SHIFT) or the coarse extent (CTRL). If the HOME key is pressed the scrollbar points the beginning of current segment it is currently positioned. Pressing the END key, it moves to the farthest possible line reachable within the same segment considering the indent.

ARROWUP and PGUP decrease position, and ARROWDN and PGDN increase position. The switch is due to the orientation of the keys with respect to the physical scrollbar on the screen. To further give you a hint, please follow the HOME and END orientation, the former being "on top" of the latter.