Most likely, all the processors you know by name are of the type: Operation-triggered architecture, or OTA. That's why the term wasn't necessary until someone decided to think differently about CPU design and came up with something called Transport-triggered architecture (TTA). Anyway, what OTA means is that the instructions fed into a processor center around the function to be performed, the operation. The operands are merely data to be manipulated by hardware according to which operation is specified. For example, something like
ADD R1, R2 could instruct the chip to do all kinds of things internally, the result being the values of registers 1 and 2 added together, then stored in R2. So it is with the
ADD that the processor concerns itself mostly, designers try to make that happen as fast as possible, of course.