Salter-Harris classification is used to describe fractures involving the epiphyseal (growth) plate of a bone. This type of fractures are commonly found in children. An easy way to remember the types is:
Salter I: Through physeal plate only
Salter II: Involves metaphysis and physis
Salter III: Involves physis and epiphysis
Salter IV: Extends from metaphysis through physis, into epiphysis
Salter V: Axial force crushes physeal plate
Note: there are an additional 4 types which were added to the original classification, making it a total of 9 types. You can read about them here.