Filler is the inside of a premium cigar. In the cigars this encyclopedia covers, it is made of long leaves, not chopped scraps. In Spanish it is called tripa. A blender builds the filler from leaves taken from different positions on the plant: volado for burn, seco for aroma, and viso and ligero for body and strength. The leaves may also come from different farms and different harvest years.
How the leaves are arranged matters as much as which leaves are used. Entubado rolls each leaf into a tube, and an accordion bunch folds them. In both cases, the goal is a comfortable draw and a burn that does not run down one side. Short-filler cigars, made from chopped leaf, are a different product.
The filler is where a company’s blending skill shows most. A puro uses filler, binder, and wrapper from one country, and a blend combines tobacco from different countries. Neither is better in principle; they are different recipes.