It came from Jamaica, and has gone through many stages. But it's summed up as good, honest music to dance (SKANK) to.
It is one of the most diverse genres, going from dreadlock-ed colored guys singing about Jah to grinning smartass punk rockers.
People that listen to ska are often happy, witty, and open-minded
"ska? ghey sir lol" - sc3n3 girl
The Specials, Less Than Jake, Operation Ivy, etc