What is the six degrees of separation theory?

The theory was the brainchild of psychologist Stanley Milgram who wanted to find the answer to the small-world problem. So in the 1960s, he conducted an experiment by mailing a packet to 160 people in and around Omaha, Nebraska, that needed to reach a broker in Boston. The findings showed that these letters reached the broker in five to six steps. This concept has been explained well in the book ‘The Tipping Point’ by Malcolm Gladwell. American playwright John Gaure is believed to have popularised this phrase by his work named after the theory, ‘Six degrees of Separation’.