Is this 400V capacitor rating for DC or AC?
So, is this capacitor DC or AC?


It's AC because it connects to the AC power mains directly (unlike an electrolytic which is polarized and should only be used on a DC system). It looks like one of these: -



Available from this not very reputable source


  Or what type of capacitor it is?


It's called a "plastic film capacitor" (possibly polypropylene) and if you google search "474k capacitor" you'll get lots of similar hits especially if you search "images".