This paper summarizes the development and evolution from digital mock-up (DMU) to digital twin (DT) by clarifying the connotation of DT from prospective of digital product definition (DPD). Firstly, taking Airbus as example, the evolution of DMU is introduced, with the detailed analysis of configured DMU, functional DMU, and industrial DMU. Secondly, based on the literature review of DT, the definition, purpose and several applications of DT concept are clearly expounded. Finally, the augmentation for DT and DPD’s relationship are deduced.