What is smog? How is classical smog different from photochemical smog?

(N/A) Smog is a form of air pollution resulting from the combination of smoke and fog. There are two primary types of smog:
$a)$ Classical smog
$b)$ Photochemical smog
The differences between the two are summarized in the table below:

Feature	Classical smog vs. Photochemical smog
Occurrence	Classical smog: Occurs in cool,humid climates. Photochemical smog: Occurs in dry,sunny climates.
Components	Classical smog: Smoke,fog,and $SO_2$. Photochemical smog: $PAN$,acrolein,$O_3$,formaldehyde,and $NO$.
Nature	Classical smog: Reducing in nature. Photochemical smog: Oxidizing in nature.