Slang is the use of informal words‏‎ and expressions to describe something or someone. Slang is vocabulary‏‎ that is meant to be interpreted quickly but not necessarily literally.

Slang changes fast; here are examples of current 2015 slang which, could well be out of date by the time you read this!
You’re mine forever, bae.
Don’t be so basic with your wardrobe.
He keeps on asking me…