A ligero leaf is harvested late, after the lower primings have already been picked. It has spent more days in the sun, so the veins are heavier and the leaf contains more oil. It dries more slowly in the curing barn, and in the pilón it heats up more and needs to be turned more often.
Rollers use ligero to add body; it is never the whole cigar. Too much ligero in a thin vitola such as a lancero can cause burn problems. A toro or robusto has more room to place a strip of it inside the seco and volado. See ligero for how the leaf is used in the bunch.
This is a farming term, not a tasting term. A ligero leaf can taste earthy, sweet, or peppery, depending on the seed, soil, and age. The priming name does not tell you the flavor.