Classic extensions are one synthetic lash to one real lash. They create a very natural look. There are many different lengths and curls.
A hybrid set is a mix of classic and volume lashes. This set is good for clients with not many lashes and its a natural look with a bit of drama.
Volume extensions are fans of 2-9 (2D-9D) lashes glued to one real lash to make it look like there are a lot more eyelashes to your eyes. Its a dramatic look best for special events or vacation.