Ligero grows at the top of the tobacco plant, where it gets the most sun and wind. The leaf is thicker, oilier, and higher in the compounds that make a cigar taste strong. In a bunch it is usually placed toward the center so it does not dominate the burn at the outside.
Because it is dense, ligero needs more fermentation and more aging than seco or volado. If it is not given enough time, the cigar tastes green and sharp. Without any ligero, many full-bodied blends taste thin. The related page ligero leaf describes the leaf as a priming, not only as part of the bunch.
Ligero is not a flavor; it is a position on the stalk. Ligero leaves from Estelí and from the Cibao valley will not taste the same. The word tells you where the leaf grew on the plant, not which farm it came from.