The shortest path between two Wikipedia articles is defined as the minimum number of clicks required to move from one article to another. This can be used to discover connections between topics that are completely unrelated.
For instance, if you are on the Wikipedia page of Microsoft, it would require just two clicks for you to reach the page of Saddam Hussein.
Six Degrees of Wikipedia is an online tool that will help you find the shortest route between any two pages on Wikipedia using links.
Unlike real world where distances remain constant if you move from A to B or from B to A, it's not so in the case of Wikipedia. The distance going from Article A to Article B is not necessarily the same as from Article B to article A.
Related: Use Wikipedia More Effectively