There were significant phases to the French Revolution. It began moderately as an effort to create the kind of constitutional monarchy (1789-1792) put together (a century earlier) by the English after their civil war, with the death of Cromwell and restoration of Charles II to the throne. The idea was to place limits on the exercise of absolute power by a sovereign monarch and place a portion of that power into the hands of an English-style parliament.
The French Revolution was, in fact, a series of upheavals, perhaps most aptly described as a major revolution followed by a series of coups d'état.
"The Terror" of Robespierre didn't happen until 3 years after the Revolution, when the government moved into a radical mode, declaring a republic and abandoning the legislative/constituent assembly. It lasted 2-3 years.
The Revolution failed in many ways - most notably when it placed Napoleon Bonaparte in power, but it had many successes too. Raymond Betts of Brittanica.com sums it up nicely:
"It is not too much to say that the ideas of the French Revolution became the measure of what later characterized modern European society, both in principle and in institution. Most obviously, the Revolution established the principle of popular sovereignty in the place of absolutism, thus replacing the dynasty with the nation. Providing the first major nation in Europe with a written constitution and a code of political behavior--this was the Declaration of the Rights of Man and Citizen--the revolutionaries, in the summer of the year 1789, had already converted the king's subject into the nation's citizen."