This conversation happens to me on a pretty frequent basis:
Person: "You're in a band? That's awesome! What type of music do you play?"
Me: "A little bit of punk rock, but mostly ska."
Person: "........what's.....ska?"
I must admit, until late high school, I had no idea what ska was! In my own words, I like to describe ska as reggae meets rock with horns added. Though lately, the genre has been shifting towards a hard rock with horns sound. Ska music is typically upbeat, exciting, and hard not to dance to. Most ska songs incorporate the "ska strumming pattern" at some point. This pattern (which is shown in one of the videos below), involves doing a down and up strum on count 1, and strumming up on the "and" of 2, 3, and 4.
1 + 2 + 3 + 4 +
D U U U U
As mentioned earlier, many ska songs sound like rock with reggae infused. Typically a ska band is made up of a full rhythm section (drumset, bass guitar, electric guitar, sometimes a synth), and a horn section (typically comprised of a trumpet, a trombone, and an alto and/or a tenor saxophone).
The following information was gathered from http://worldmusic.about.com/od/genres/p/Ska.htm. Ska has transformed over the years. Traditional ska originated in the late 1950's in Jamaica and thus sounded very reggae infused. Two-tone, or Second Wave ska, was introduced in the late 1970's in England when musicians started to fuse reggae with the "brand new" (at the time) genre of punk rock. Ska as we know it today is currently in the Third Wave, and gained popularity in the late 1980's and 1990's with bands like Reel Big Fish, No Doubt, and Goldfinger. The focus shifted to larger horn sections and dominant guitar riffs which shifted the music to focus on alternating upbeats during part of the song and driving downbeats for other parts of the song.
The video shows you how to play a couple of basic ska strumming patterns. Have fun!
For a chance to hear one of the ska patterns I played in a real song (and many others as well), check out Reel Big Fish's cover of "Take On Me"!