No worries man, it's all about building your own coils as compared to buying replacement ones that you would put in a kanger tank for example. Or buying a new clearomizer tank when one wears out.
With sub ohm vaping, you are creating a coil around a wick that when tested on an ohm meter, it reads at less than one ohm of resistance.
With sub ohm coils, you have say, 3.8 volts coming from your battery into a coil that has very low resistance which results in more vapor and usually more flavor. The problem is that if you dont know how much drain your sub ohm coils is placing on your battery, bad things can happen. This is why people use an ohm's law calculator to determine if your battery can provide the proper power to the coil you built.
Higher resist coils like 1.5 and 2.5 ish that come with replacement prebuilt coils don't put as much stress on batteries and are just fine but cloud chasers get into sub ohm to get as big of a cloud as they can. I myself use them to get even more flavor out of my juice.