The subjects of virtual machines and emulators have been treated as entirely separate. The purpose of this seminars is to show they have much in common. Only the usual implementations have many shared characteristics, but this extends to the theoretical concepts on which they are based; the concepts of memory mapping and I/O operation simulation are discussed to emphasize this. It also discusses structural issues, and points out why the question of instruction set is becoming less valid as a point of distinction between the concepts, It is then discusses possible similarities, differences of virtual machines and emulators are discussed. In conclusion, it is recommended that developers in both fields keep the relationship between these two in mind. At the end it introduces some recent developed virtual machines and emulators.