The star Achernar is the closest Be star to Earth. Be stars are hot and luminous stars (though less then Eta Car ior Gamma Vel) which are at the middle of their lives. They exhibit sometimes emission lines of hydrogen and other metals (« metals » for astronomers start from the element Helium). If you have no idea of what is an emission line, you can have a look here to the emission-less spectrum of the Sun here, and the spectrum of an emission-line star there. The second one shows a