As the commercial goes, "What's in your blend?" Or was that wallet?

There are quite a few basic types of baccy leaf that are, well, blended into our much loved blends. Often a topping is added to, well, top the mixture. The combination of tobacco types and topping(s) (if any) are what gives each blend its own uniqueness.

Virginia tobacco has a natural sweetness due to its sugar content, but tends to give "tongue bite" due to its chemical composition and burn characteristics. Mostly VAs are mixed with other types to reduce the bite, yet retain the flavor. Virginia ages well, cellaring results in a smoother smoke, especially after many years of aging.

Another technique used to tame virginia is to "toast" or "cook" it (called stoving), this results in the type called Cavendish. While more mellow than VA, the taste tends to be sweeter.

Burley is probably the most used tobacco type. Many aromatic blends use burley as a base, mainly because burley tends to take of the flavor of whatever it is added to. While simple aromatic blends do not age too well (the toppings break down and go poof), burley and virginia blends do indeed age very well. Esoterica Tobacciana's Stonehaven for example, ahhh heaven, at any age.

Perique is a condiment type leaf, depending on what it is blended with and how much, perique can go from a scorching spiciness to a figgy sweetness. Escudo, of course, is the flagship of a VA/Perique blend.

Oriental leaf adds a herbal/salty/spicy taste, depending on the type used. Latakia is technically a kind of oriental tobacco, but is flavored by burning herbs to give it the unique barbeque smokiness making it a different animal.

Aromatics are generally classified as blends that have an added artificial flavor topping that completely overwhelms the true flavor of the base tobacco.