Mission setup for terrain following

I now have Mission Planner 1.3.41. I tried to find documentation on the ‘Waypoints’ table in Flight Plan, but have found nothing.

In the header there is ‘Default Alt’ which I don’t fully understand.

Next to the above is a drop down box with options: Relative; Absolute; Terrain. My question for this is: when flying a mission over terrain with distinct altitude changes, i.e, hills, which is the correct/best option to choose. Should it be ‘Relative’ or ‘Terrain’?

I have checked the ‘Verify Height’ box, which I understand does enable terrain following. Is this correct?

A clear elucidation would be really appreciated.

Thank you in advance

http://ardupilot.org/copter/docs/common-mission-planning.html

Thank you Dave, I missed the Terrain section when looking earlier. Doh!