Hi there, basically sub ohm vaping is when you build your own coil/wicks that when tested on a ohm meter read out at less that one ohm resistance.
Let's say you are using basic clearomizer tank on an ego style battery like this
Those wicks you see in there.... at the top of them is some wire wrapped in a coil around the wick.
The juice is pulled up through the wick and onto the coil so that when you hit the button on your battery the coils light up red hot and vaporize the juice. These clearomizers like most usually have a resistance of around 1.5-2.5 ohms
With sub ohm vaping, people like myself use a rebuildable atomizer like this where we build our own coils/wicks that read out at less than one ohm
The main reason people sub ohm vape is for massive vapor and flavor production but you MUST know your battery safety and how sub ohm vaping relates to the batteries you are using so nothing bad happens.
here is just a random video I found with some info on sub ohm vaping, It's early for me so I hope I made sense lol post questions if I missed something.