Need I say more? OK, maybe I do.
There are too many different kinds of leather to even try to go into on this site. Suffice it to say, there is a type of leather for every purpose, from super-thick leather for shoe soles, to super-thin leathers used for linings and veneers. As well as numerous weights (thicknesses) there are types from different animals, different colors and color patterns, different tanning and preparation methods (like latigo and suede), something for everything!
I tend to stick with medium weight tooling leather. It can be colored to suit, tooled and prepared in many ways. Also, the kind of leather work I do calls mainly for tooling leather. Besides tooling leather, the only other type I get very often is lining leather which I use for linings and interiors of projects.