Before the Arab Spring of 2011, political unrest in Northern Africa (this was the place where the Arab Spring began and where it had the greatest effect) was mainly latent. There were times and places where there was active unrest, but much of the political unrest was just in the form of unhappiness on the part of the people. It was waiting for some sort of catalyst to make it truly begin.
In December of 2010, a Tunisian man named Mohamed Bouazizi set himself on fire in protest because a corrupt government official had confiscated the fruit he had been selling. This served as a catalyst for the unhappiness in Tunisia. Massive demonstrations followed and the President of Tunisia fled the country less than a month later.
Bouazizi’s action and the protests that ensued also served to inspire similar demonstrations across much of the Arab world. Much of the Arab world had been under undemocratic and often authoritarian rule (for example, that of Quaddafi in Libya) for decades. This had made many of them very unhappy since they had few rights and, in many places, poor economic situations. With modern technology (internet, satellite TV), Arabs quickly became aware of the protests in North Africa. This led them to seek redress for their own grievances. In this way, political unrest in North Africa led to the Arab Spring.