There are various extension techniques classic, 2D, 3D, 4D, 5D, etc.
Classic extensions involve attaching one artificial lash to each natural eyelash. 2D, 3D, 4D and 5D are volumetric extension techniques where 2, 3, 4 or more artificial lashes are attached to each natural eyelash respectively.
You can also add effects to your extensions - KIM, PERFECT LINE, WET EFFECT, COLOR EFFECT