Are Dual 4 Ohm Subs considered 8 or 4

im just a bit confused about the terminology here. I got 2x Kicker 4 ohm Dual Voice coil subs are they considered 4 ohm or 8 ohm subs

They're considered dual 4 ohm subs.  Each one can be wired either to 8 ohms or to 2 ohms.  See http://www.rockfordfosgate.com/rftech/wiringwizard.asp?WoofQty=2+woofers&WoofImp=Dual+Voice+Coil+-+4+ohms+x+2&image.x=21&image.y=11

so can some subs not be "dual"?

SVC (single voice coil) subs are the original type of subwoofer...just like all speakers are made.  The dual-type voice coil on subwoofers is a fairly recent development that helps buyers match sub + amps + power better as they make wiring to certain impedances a little more flexible.  You'll find SVC subs, and then you'll find DVC subs with 2, 3, 4, 6 and 8 ohms per coil.  The majority are dual 4 ohm.  Here are some past posts on the subject:  https://www.the12volt.com/installbay/search.asp?KW=coil&SM=1&SI=TC&FM=2&OB=1&Submit=Start+Search