This Wikipedia page on semicolon has a special paragraph for French. But in my reading of it, the French use seems to be the identical to the use in English. I do not understand the distinction being made specifically for the French language.
In French, a semicolon is a separation between two full sentences, used where either a colon or a comma would not be appropriate. The phrase following a semicolon has to be an independent clause, which is related to the previous one (but not explaining it, contrary to a sentence introduced by a colon).
The dash character is used in French writing too, but not as widely as the semicolon. Usage of these devices (semicolon and dash) varies from author to author.
➠ How is the use of semicolon in French different than in English?