This is an herb spiral, in which you plant drought hardy plants at the top and water-thirsty plants at the bottom. By adding wood, it mimics hugelkultur, in which buried wood adds nutrients and reserves water. - Grow Food Not Lawns Facebook page (link goes to "15 Reasons a permaculture herb spiral lets you practice sustainable gardening in urban or country settings" by NaturalNews)
How to cut herbs - for basil don't pluck leaves off, instead trim stem. Leave two sets of leaves on stem (leaves grow in pairs across from each other). Cut immediately above the second set of leaves from the ground. Plant will then grow new branches from this cut.