Here is a little insight into the world of leather, as well as the leathers that I use (and why I use them). To the untrained eye, the terms below are almost interchangeable. In reality, there is a big difference.
Full grain leather
The top part of the hide, full grain leather holds its shape the best, is the strongest and most durable. It is considered to be the highest quality leather available and is what I use for my leather crafts.
Sometimes there will be natural markings like scarring, bug bites, and stretch marks. These small markings are part of what adds character to high quality leather goods. Another feature that adds character to full grain leather products is the ability to absorb moisture and oils to develop a beautiful patina over time. Don't be surprised if full grain leather lasts longer than the thread holding it together.
Top grain leather
Top grain (or corrected grain) leather is actually full grain that has been buffed back of any imperfections to provide a very uniform look. Top grain is still high quality, although it is considered that it may not be as durable as full grain due to losing some of the outermost grain as part of the "correction" process.
The term seems to have been hijacked by marketers who prefer to say "genuine" instead of "cheap". This leather is generally made with scraps and layers of split leather glued together with polyurethane or vinyl. It has less memory and doesn’t hold its shape as well. Genuine leather is the most common type of leather used in products from big name brands that sell in big box stores.
Bonded leather is also in this category. It can contain as little as 20% actual leather fibers and generally develops cracks and peels.
So, while "genuine leather" is real leather, it is generally of a cheaper quality than the rest. This type of leather is reasonable enough for some things, but not for carry goods.
What is vegetable tanned leather?
Vegetable tanned leather has a long history and is the most traditional form of tanning leather. The leather is not processed with chemicals but rather with natural materials such as tree bark, thus making it the most eco-friendly option when it comes to leathers.
Vegetable tanned leather is considered higher quality and will last longer than synthetically treated leather. It takes at least 28 times longer to make which is part of the reason why vegetable tanned leather only makes up roughly 10% of all leather available today.
Tanneries producing vegetable tanned leather must use all natural, raw materials and ensure that no animal is killed for its skin.
I use full grain vegetable tanned leather for all of my leather goods. Some of the leathers I use include, but are not limited to: Buttero (by Conceria Walpier), Gaucho (by Conceria La Bretagna), Maremma and Italico (by Conceria Puccini Attilio), Pueblo (by Badalassi Carlo tannery), Shell Cordovan (by Rocado and Shell Cordovan Toscana Italia).