gius said:
Colour palette can just mean what colours have been used to make something.
He hit the nail on the head. Look at say... the Coca-Cola logo. The palette is red and white.
Pepsi? Red, white and blue.

< that smiley? Looks like yellow and red, and the blends within.
It's really the base colors, and usually you want it to be harmonic, like 'Earth' tones (oranges, browns, tans, etc) or 'cool' tones (blues, greens, greys maybe.)
Once you get a nice harmonic balance, then you can pull other colors out of it for accents, etc. Don't study color theory too hard though, rules are made to be broken. And if you go by the book, you'll look like everyone else. Think of a palette as swatches of color like in a book of paint chips. Pick the ones you want and go from there.
BTW, the guy that taught me color theory is color blind.
