The circle never stops, it just keeps going around in circle. The circular argument is easier to understand when its named “assuming the conclusion” it is very common among ideologues, and the “sound-snippet” crowd.
It’s effective because it often sounds good because of the way it has been worded, and because the conclusion becomes self-reinforcing.
A very easy example is:
Premise: The Bible is the absolute word of god and infallible.
Conclusion: The Bible is infallible because it is the word of god.
In this case, the conclusion is just the premise in a slightly different order.