This is a duet between will.i.am from the Black Eyed Peas and actor/singer Jamie Foxx. The song is from the soundtrack for the computer animated film Rio, which is set in the Brazilian rainforest. Both stars voice characters in the movie: will.i.am plays a cardinal named Pedro and Foxx is a canary called Nico.
The song is built around the repeated refrain, "I wanna party, I wanna samba," and is about partying, dancing and living life to the fullest. It finds Foxx and will.i.am trading verses, in character as their Rio likenesses.
"Piano Man" was inspired by Billy Joel's time playing at a piano bar in Los Angeles. The "real estate novelist" was a guy who always talked about writing a book, but spent all his spare time in the bar.