The main causes of the French Revolution were:
1) The French Peasants had to pay all the taxes to support court extravagances and war campaigns and pensions of the nobles.
2) French masses were bankrupt
3) There was a general feeling among the people that a change must be brought
4) Peasants were starving
5) The First (priests) and the Second State (nobles) could always veto the recommendations given by the Third Estate (common people) so the Third Estate declared that they were the National Assembly : The Real rulers of the country.
They were weak so the king drove them out bu they continued to meet in an indoor tennis court where they vowed not to separate until a constitution was set up.
The significance of the Revolution was the Declarations of the Rights of Man . a document that still is the basis of most democracies today. The national Assembly said that everyone had to pay taxes. People started dressing in high and modern fashion and the fashion industry flourished. If you want more details then ask :)