Mouth Piece: This is the part that goes in your mouth. It is interchangeable mouthpiece.
Tank Or Clearomizer: E-Liquid & atomizer (heating element) are held within this part of the device.
Coil Head : A metal coil around wicking material, usually cotton or silica, needs to be changed every now and then, usually somewhere between few days and a couple of weeks.
Button: Power the electronic cigarette on & off. the atomizer to be fired, hence heating the e-liquid and converting it into vapor clouds.
Battery: This contains the electronics and battery needed to heat your coil. Battery capacity is denoted as milliampere hour (mAh).