Begging the question (or petitio principii, "assuming the initial point") is a type of logical fallacy in which the proposition to be proven is assumed implicitly or explicitly in the premise.
The first known definition in the West is by Aristotle around 350 BC, in his book Prior Analytics, where he classified it as a material fallacy. Begging the question is related to the circular argument, circulus in probando (Latin, "circle in proving") or circular reasoning, though these are considered absolutely different by Aristotle.
Please go to the original link because this one has beocme so complicated over the centuries that; “Academic linguist Mark Liberman recommends avoiding the phrase entirely, noting that because of shifts in usage in both Latin and English over the centuries, the relationship of the literal expression to its intended meaning is unintelligible and therefore it is now "such a confusing way to say it that only a few pedants understand the phrase.”
At this point I am going to jump ahead to “(shifting the) Burden of proof (see – onus probandi) – I need not prove my claim, you must prove it is false.”
This will take you to a number of explanations, but this is the one most of us will deal with. Philosophic Burden of Proof.