Tanks are the part of your vape that holds your eliquid and houses the coil that vaporizes your eliquid. Most tanks have a pyrex glass middle component that allows you to see how much eliquid in left in your tank, to avoid vaping all the liquid and burning your coil out. Most vape tanks on the market are designed to be top fill, which allows you to fill the tank up while it is still attached to your vape device. As well as being able to be easily refilled, vape tanks come in a wide variety of sizes (each holding different amounts of liquid) each with their own characteristics. Sub-Ohm vape tanks are tanks that have vape coils that have a resistance lower than 1.0 ohms which allows you to fire your device at a higher wattage.
Most vape tanks Gorilla Vapes carries are 510 threaded and designed for use with most other 510 threaded vape mods.