Slang is a type of jargon that originates from various small groups of people. They tend to come about from conversation, and people naturally use words that have a meaning for them, then over time, these words alter and become slang.

It is probably one of the hardest aspects of the English language to learn, because there are so many variations in each small town, let alone in different English-speaking countries!

People use slang to sound less formal. Slang is mainly used because it relaxes the mouth, and allows people to speak in a more comfortable way. It is a lot easier to use slang than ‘perfect English’, which is probably why it’s so common!

Data taken from: http://www.espressoenglish.net/slang-words-food-and-drink/