General objective of this article is to Define and Discuss on Mass Spectra. In a mass spectrometer, a solid or fruit juice is heated under lessened pressure to convert it in a gas. The molecules on the gas are then exposed to high‐energy electrons. Collisions between the gaseous molecules along with the electrons convert a few of the molecules into positively charged ions. Here also briefly discuss on Integral molecular weight and Fragment and rearrangement ions.