The guillotine was the main method of execution during the French Revolution. It continued to be used in many countries long afterwards. In France it remained in use until the abolition of capital punishment in 1981.
The guillotine is named for Doctor Joseph-Ignace Guillotin, who, in 1789, persuaded the National Assembly that they needed to make the practice of capital punishment more equitable and humane. As the French Revolution progressed, the need for an efficient means of dispatching people from the world became increasingly pressing. The National Assembly resolved that the mechanism for death should be restricted to ending of life, rather than infliction of pain (unlike, say, the breaking wheel). It appointed a committee to come up with an appropriate mechanism. The committee, drawing inspiration from head-crushing/chopping devices then in use in Britain and Italy, commissioned Tobias Schmidt, a German engineer and harpsichord maker, to construct a prototype of what was subsequently christened the guillotine. It was quickly put to use - the first execution by guillotine was performed on a highwayman on 25 April 1792.
If one had to be executed, the guillotine offered a fairly attractive option. Previously, a member of the nobility would have been beheaded with a sword or axe (which took at least two blows), while commoners were usually hanged, unless they were unlucky enough to get the wheel or be burnt at the stake.
Estimates of the number of people sent to the guillotine between June 1793 and July 1794 range between 16,000 and 40,000.