So, what’s the point of these puffy white things? How comfortable is it? Is there a reason why clowns wear it, or do clowns wear it because it looks so ridiculously goofy? 
They are called ruffs.
Why anyone would wear there is beyond me.
Style is inherently arbitrary. Why earrings & not chin-rings? Bare shoulders are sexy; bare elbows are meh.
In Europe & North America through roughly the 1600s-1800s the predominant style was for the male of the species to be the clothes horse, while women dressed more plainly. At least this was true for the wealthy. Poor folks all dressed like nothing.
And there was a certain fashion for difficult clothes which demonstrated self-discipline in the wearing. Sorta the same function which high heels have today.
Originally for the same reason some men used to wear shirts with detachable collars. Your neck can get sweaty if you’re wearing clothes which are fitted close around the neck and this then shows up as dirt. A ruff had the advantage that it could be washed (and starched) separately. This was especially important in the sixteenth and seventeenth centuries, when the fabrics used for fashionable outer wear usually couldn’t be washed at all.
Of course, once people began wearing ruffs for this practical reason, the styles quickly become extremely elaborate as fashion statements.
Clowns wear them because of the influence of Commedia dell’Arte.
One of my theater teachers said that Cyrano de Bergerac is often portrayed with an extremely starched ruff, which forces him to keep his neck very straight. He is always on the alert for danger and for ladies that need poems written for them, so his ruff helps keep him on his toes. If this were a common thing in the culture, it lends credence to the “discipline” idea in post #3. (Then again, Cyrano is supposed to be anything but common!)
They give talking dogs something to talk about.