Basically it's the same as Levi's vs blue jeans, all Levi's are blue jeans but not all blue jeans are Levi's . Ultram is made by Ortho-McNeil and is the patent holder. Tramadol is essentially the same drug as Ultram that's manufactured by several other companies.
Tramadol is generic for Ultram, a non narcotic anti-inflammatory. Ultracet is a combination of ultram and acetaminophen (tylenol.) Hence the ET at the end of the name. BAsically, one contains tylenol, once does not.