Short answers, pulled from the story.
The Romance languages are the languages that directly descended from Vulgar Latin, the spoken language of the Roman Empire. They are the only extant subgroup of the Italic branch of the Indo-European language family. The five most widely spoken by native speakers are Spanish, Portuguese, French, Italian, and Romanian.
There are more than 900 million native speakers of Romance languages worldwide. Spanish accounts for roughly 54 percent of that total, with about 475 million native speakers, followed by Portuguese at around 230 million and French at around 80 million.
Romance languages spread globally because of European colonialism beginning in the fifteenth century. Portugal, Spain, and France established colonial empires that carried their languages to the Americas, Africa, and Asia. Today roughly two-thirds of all Romance language speakers live outside Europe.
By most measures, Sardinian and Italian have changed the least from Latin. Sardinian in particular preserved a simple five-vowel system close to the original Latin vowel inventory. French has changed the most among the major Romance languages.
Latin reached a stage of widespread innovation around the sixth and seventh centuries, after which speakers of the Romanized regions could no longer understand texts read aloud to them in Latin. By the eighth and ninth centuries, Romance had effectively replaced spoken Latin. The Council of Tours in 813 formally acknowledged this, ordering priests to deliver sermons in the rustica romana lingua rather than classical Latin.
Yes. The UNESCO Red Book of Endangered Languages classifies virtually all minor Romance languages as threatened. Sicilian and Venetian are listed as vulnerable, while Franco-Provencal and most Occitan varieties are listed as severely endangered. Some varieties, such as Dalmatian, have already gone extinct, with its last recorded death in 1898.