This is from the Horween Leather website:
CHROMEXCEL®
Chromexcel is the original pull-up leather; using time honored techniques and formulas that were developed nearly 100 years ago. Chromexcel is still produced in the United States using a bark retannage from a proprietary recipe, and then genuine hot stuffed with our secret blend of natural oils and greases. Chromexcel is characterized by a rich pull-up in full aniline, hand rubbed finishes. Made to this day with old world craftsmanship, modern Chromexcel carries on a long history of superior comfort and durability.
And if that is not confusing enough...
ESSEX
Essex is a vegetable tanned side leather that utilizes the same traditional tanning extracts as our Genuine Shell Cordovan. Essex, and its waxed versions, Dublin and Derby, took us nearly three years to develop and perfect. This tannage is marked by a high oil content and ages beautifully over time. The Essex family of leather is very versatile and can be used in a wide variety of products.
And then there's this, from the Maverick Leather website:
Latigo leather is best described by our friends over at The Tannery Row:
“Horween Latigo is a combination tan that blends the durability of a chrome tan base with a heavy veg re-tan to create an unfinished, natural look that’s excellent for molding. It holds embosses well, retains molded shapes and has both full and corrected grain versions.”