Classification systems provide organization for pathologic conditions and guide treatment for similar disease states. Spine deformity is a growing field with newer classification systems being developed as our surgical techniques and clinical understanding advances. The evolution of these classification systems reflects our current knowledge and are used to better understand the evolving field of spine surgery. Currently, classification systems in spine surgery range from describing deformity in different age groups and different regions of the spine to describing various osteotomies and the severity of proximal junctional kyphosis. This paper will describe what makes a successful classification system in spine deformity. Old classification systems will be briefly described and their limitations that necessitated the need for newer classification systems. Newer systems will also be reviewed and the importance of specific radiographic parameters. Finishing this review, clinicians will be able to pick which systems are ideal for their practice.