Apples are important from both a cultural and nutritional standpoint. The fruit produced from the cultivated apple, Malus × domestica Borkh., is grown in temperate regions throughout the world. Ornamental crabapple trees represent other Malus species and are generally valued for their landscape properties rather than their fruits. Genetic analyses of apple cultivars and species have revealed domestication pathways, pedigree relationships, as well as data that guide genebank collection management practices. Molecular information is also critical for breeding programs that are using new techniques to identify novel genetic combinations with enhanced biotic and abiotic stress resistance as well as desirable fruit quality and production traits. This chapter includes information about wild apple species, origins of cultivated apples, genetic assessments, as well as some basic information about tree phenology, architecture, and propagation methods.