What is the difference between AC and DC capacitors ?

There are no specific AC or DC capacitors.  All capacitors can be used in DC applications.  In AC applications, only non-polarized capacitors which do not have polarity should be used.

Electrolytic capacitors are examples of polarized capacitors. These capacitors have a fixed polarity and should never be used in AC circuit as there is a risk of the capacitor exploding.

Other capacitors such as paper capacitors, film capacitors, air capacitors are non-polarized and can be used in both circuits.