This talk will cover the basics of phase change memory technology including the switching properties of chalcogenides, characteristics and timing parameters, cell types such as a confined cell characteristics, multi-level cell characteristics, access transistor types, and scaling issues. An overview of various issues associated with these memories will be given such as resistance drift due to structural relaxation, crystallization behavior, write current optimization, oscillatory behavior, electromigration, and phase separation.  Various applications that have been proposed will be considered along with potential substitution for conventional memory types.