The Digimon TV show has two seasons and only one of them has been seen in north America.  The first season can be divided into several sections, each one being named after the villain or villains of the time.  The "eras" are: Devimon, Etemon, Myotismon, and Dark Masters.  The Dark Masters Era can be dived into four sub-eras, they are: Metalseadramon, Puppetmon, Machinedramon, and Piedmon.  For Season 2 info, click here.