The Sega Dreamcast was Sega's last best hope as a console maker after their Sega Saturn tanked badly. Released in 1998, it was the first of the sixth generation systems, the first major console to come with a modem and online play capability, and was far superior to not only everything then on the market, but was in many ways better than the systems that would eclipse it.
Less than a year after a highly successful release, the Playstation 2 came out and that was really the end of the console wars for a long time. The PS2 is the highest selling system ever, and Sega simply couldn't stay in the system business that now had not only their old rivals Nintendo, but giant corporations like Sony and Microsoft. The Dreamcast was quietly discontinued in America in 2001.
Still, it left behind a legacy, and several interesting tidbits that you may not know.