Coils or Atomizers as they are also known are where the magic happens within your vape tank. Coils are the replaceable piece at the heart of your tank where eliquid is heated to the point of vaporisation. A coils is as the name suggests a coil of wire that is wrapped in an organic cotton wicking material which draws the eliquid into the coil, when you push the trigger on your device the coil activates and the battery heats up the coil to vaporize your eliquid.
Coils are available in various resistances (measured in ohms), which allows you to tailor your vaping experience to your particular needs and tastes. Sub ohm coils (below 1.0 ohm) allow for more current to flow through, which heats the coil at a higher temperature which produces warmer and larger amounts of vapour. Alternatively higher resistance coils do not allow as much current to flow, which creates less heat and a cooler vape. Some coils are Claptonised, these increase the surface area of the coil by wrapping a thinner gauge wire around the main wire, this in theory increases vapour and flavour production.
Coils also come in several different materials to suit different styles of vaping. Kanthal, Stainless Steel, Ni200 (Nickel), Titanium, Nichrome etc. You should refer to the capabilities of the devices you own or are thinking of buying to understand exactly which sorts of coils it can control.
Please note: Each coil will only fit a specific model or brand of tank so please carefully check the product listing for its tank compatibility.