Single layer or Classic lash technique is the process of applying 1 lash extension to 1 natural lash, 1:1. This techniques provides depth, length and the appearance of having applied mascara to a set of healthy lashes. 

Volume lash technique is the process of applying multiple lash extensions to 1 natural lash , all the while not exceeding what the natural lash can withstand. This techniques provides texture , fullness and drama.