R+ trees are a compromise between R-trees and kd-trees: they avoid overlapping of internal nodes by inserting an object into multiple leaves if necessary.
Coverage is the entire area to cover all related rectangles.
[1] Minimal coverage reduces the amount of "dead space" (empty area) which is covered by the nodes of the R-tree.
Efficient search requires minimal coverage and overlap.
A single path is followed and fewer nodes are visited than with the R-tree.