Mark Foster is the lead singer, writer and guitarist for the group. When interview he said that he likes to write songs that are "true to life" - about real topics and situations. And although the music is quite dance-able and happy the lyrics are often quite depressing.
For example - "Pumped Up Kicks" is about a homicidal teen who smokes and steals.... not exactly happy but hey! I can dance to it :)
Although they're considered genre bending spanning indie, dance, and pop. They're wiki page calls their music "melodic dance-infused pop and rock". Foster has written songs in pop, indie, electronic, and piano genres.
They've been nominated for Best New Artist, Artist of the Year, Best New Act and a few other variations of being awesome at the Grammy's, MTV Music Awards, and BRIT Awards.
My favorite song is "Houdini" and you can check them out here! I give Foster the People 4 out of 5 stars. Their next album will tells us if they have staying power and possibly up their rating.