How do Catholics describe "eternal generation"?

It seems to me that "eternal generation" is an oxymoron : > "a combination of contradictory or incongruous words (as cruel > kindness); broadly : something (as a concept) that is made up of > contradictory or incongruous elements" It seems to me that "generation " requires at least a single step: > a : the action or process of producing offspring : procreation b : > the process of coming or bringing into being c > : origination by a generating process : production; especially : > formation of a geometric figure by motion of another Do they say: * God and Jesus both existed eternally with Jesus "describable" as a son, begotten, etc. but with no actual, literal birthing having occurred? * the begetting of Jesus occurred so long ago as to be for all intents and purposes to still be considered "eternally so"? * it is a "mystery beyond human comprehension" (as the Trinity in general is often described)? Or do they simply use the term without explanation of the contradiction?