What does this phrase mean? I'm reading a paper and at some point the author writes : 

"We do this by decomposing monthly real crude oil prices and analyzing the
effect of the smooth part on the degree of the stock market instability."

What does he mean by "smooth part"? Is it the same meaning we have when dealing with integers?(factoring to prime numbers) Or is it something else? I don't understand what "the smooth part" means and how it is of any importance.

Sorry in advance if the question is too beginner.
I'm guessing the author has split the series between a trend component and noise component, for example with the HP-filter, and studies the smooth trend component.