A small-world network is a graph characterized by a high clustering coefficient and low distances. On an example of social network, high clustering implies the high probability that two friends of one person are friends themselves. The low distances, on the other hand, mean that there is a short chain of social connections between any two people (this effect is known as six degrees of separation).
![Small-world network - Wikipedia](https://cdn-ak-scissors.b.st-hatena.com/image/square/da50f348b73ef42c33bed0627e3657c94fac41c2/height=288;version=1;width=512/https%3A%2F%2Fupload.wikimedia.org%2Fwikipedia%2Fcommons%2F3%2F37%2FSmall-world-network-example.png)