Esperanto is a constructed language, invented at the end of the 19th century by the Polish-Jewish ophthamologist L. L. Zamenhof.
He believed that the division between the various ethnic groups in his city of Białystok could be overcome if they shared a language, and he published Unua Libro (First Book) describing the language he had been working on in 1887.
The language originally grew in Eastern Europe and Russia, but spread to Western Europe and the first Universal Congress of Esperanto took place in France, in Boulogne-sur-Mer, in August 1905.
Since then, a Universal Congress has taken place every year (except for during the World Wars), with the 100th again in France, taking place in Lille in 2015. Many other conferences, meetings, groups and organisations have since come about, some specifically for the promotion of Esperanto, and some merely using it as a culture-neutral working language.
The language itself takes words from a range of European languages, including French, Italian, German and English, and its grammar is highly simplified and regular. It is possible to reach a working knowledge of the language in a fraction of the time it might take to learn a natural language like French or German, and new words can easily be invented and understood by use of the system of prefixes and suffixes with fixed meanings.