In a nutshell, and lifted from good ol' Wikipedia, here is 'Bastille Day' : (*My comments in blue*)
On 5 May 1789, Louis XVI convened the Estates-General to hear their grievances. The deputies of the Third Estate representing the common people (the two others were clergy and nobility) decided to break away and form a National Assembly.
*They broke away because the other two estates, though they represented only about a fifth of the population, always voted together and made all the laws. The people's representatives were powerless and decided to take matters into their own hands.*
On 20 June the deputies of the Third Estate took the Tennis Court Oath, swearing not to separate until a constitution had been established.
*It's called the tennis court oath, (jeu de paume, in French) because they gathered in an indoor 'jeu de paume' court.*
They were gradually joined by delegates of the other estates; Louis started to recognize their validity on 27 June. The assembly re-named itself the National Constituent Assembly on 9 July, and began to function as a legislature and to draft a constitution.
In the wake of the 11 July dismissal of the royal finance minister Jacques Necker, the people of Paris, fearful that they and their representatives would be attacked by the royal military, and seeking to gain arms for the general populace, stormed the Bastille, a prison which had often held people arbitrarily jailed on the basis of lettre de cachet. *The army had slowly been gathering in Paris, and armed soldiers were starting to make the populace very nervous. They decided to arm themselves. They had the guns, but lacked the gunpowder.*
Besides holding a large cache of arms (and gunpowder), the Bastille had been known for holding political prisoners whose writings had displeased the royal government, and was thus a symbol of the absolutism of the monarchy. As it happened, at the time of the siege in July 1789 there were only seven inmates, none of great political significance.
When the crowd (legend says it was organised by descendants of Knights Templar)— eventually reinforced by mutinous gardes françaises — proved a fair match for the fort's defenders, the commander of the Bastille, Governor de Launay, capitulated and opened the gates to avoid a mutual massacre. However, possibly because of a misunderstanding, fighting resumed. Ninety-eight attackers and just one defender died in the actual fighting, but in the aftermath, De Launay and seven other defenders were killed, as was the 'prévôt des marchands' (roughly, merchant mayor) Jacques de Flesselles.
The storming of the Bastille was more important as a rallying point and symbolic act of rebellion than a practical act of defiance.
Shortly after the storming of the Bastille, on 4 August feudalism was abolished and on 26 August, the Declaration of the Rights of Man and of the Citizen proclaimed.
And there you have the origins of the Bastille Day celebration in France! Our village is going all out this year, and the celebrations are planned for the whole weeked. On Saturday, there will be fireworks. And on Sunday, a dinner/dance is planned for the village square!