In pinnate venation, the veins extend laterally from the midrib to the edge, as in apple, cherry and peach. Palmate venation occurs in grape and maple leaves, where the principal veins extend outward, like the ribs of a fan, from the petiole near the base of the leaf blade. (The University of Arizona)

Parallel venation occurs in the leaves of nearly all monocotyledonous Angiosperms, whose embryos have one cotyledon, as in flowering plants such as lilies and grasses. (Net Industries )

Recent work has shown that this diversity in venation has consequences for leaf and whole-plant hydraulic capacity, for leaf biomechanical support, and for leaf tolerance of vein damage. (eco.confex.com)