Do you know what a monarchy is? Very simply, it is a form of government that is led by a ruling family - often, a king and a queen. If you've read storybooks, you've probably heard of this kind of government. In many books, kings and queens are good people. Their subjects (the people who the king and queen rule) love them. While this is true in many books - and in reality sometimes - it wasn't true for French citizens in the 18th century. The French hated their king.
King Louis XVI wasn't a good leader for his people. As king, the economy sank and national debt grew. The structure of a monarchy ensured a good life for rich people and a worse life for poor people. This was especially true in Louis XVI's time. Then there was Louis XVI's wife, the queen.
Marie Antoinette wasn't French, but Austrian, by birth. This fact alone caused many French citizens to hate her. Her marriage to Louis XVI was arranged to strengthen the French and Austrian alliance. Marie Antoinette enjoyed her life as queen. She spent lots of money on very nice things. Too much money, many French people thought. There were also rumors that Marie Antoinette had many lovers.