Shortened form of 'application.' Popularized by Apple Computers Inc. with the introduction of the iPhone. Mainly implemented because the majority of the Apple userbase is too retarded to even be able to use two mouse buttons, let alone pronounce a four syllable word.
Starbucks drinker: "I just downloaded this great app for my phone. It's called Super Monkey Ball! This is exactly why I love the iPhone!"
Starbucks employee: "I made the cream in your coffee."