They have been around since 1996 and have put out six albums, as they have grown in popularity and their line up has changed the music has inevitably changed too - it's become more mainstream with influences from Reggie to Country. They even did a song with K-pop band Big Bang and they have made songs for the Korean teams in the Soccer World Cup over the years. The members have also appeared on a few TV shows in acting and hosting jobs.
So here is one song I have picked to showcase off YouTube, it was a bit of a random selection but there are many others so if you are interested check them out. You can also find the band on Facebook and their official site.
No Brain - 넌 내게 반했어
info from Wikipedia