Short answers, pulled from the story.
According to Constantine Porphyrogenitus's De Administrando Imperio, Dubrovnik was founded in the 7th century by refugees from Epidaurum, a Roman city located approximately 15 km to the south that was destroyed by Slavic forces allied with the Avars. The earliest settlement was built on a rocky island called Lausa.
The two names coexisted for centuries because they came from different linguistic traditions. Ragusa, recorded since at least the 10th century in Latin, Dalmatian, and Italian, was the official name of the republic until 1808 and remained in use within the Kingdom of Dalmatia until 1918. Dubrovnik, first recorded in the Charter of Ban Kulin in 1189, derives from a Proto-Slavic root meaning oak or oak forest and became widespread by the late 16th or early 17th century.
The Republic of Ragusa governed itself as a free state from the 14th century until 1808, when Marshal Marmont issued a proclamation abolishing it and absorbing its territory into the Napoleonic Kingdom of Italy. During that period, from 1382 to 1804, the republic paid annual tribute to the Ottoman sultan while maintaining its independence.
The siege, which began on the 1st of October 1991 and lasted seven months, resulted in 114 civilian deaths according to the Croatian Red Cross, with the heaviest single day on the 6th of December killing 19 people and wounding 60. Artillery attacks damaged 56 percent of the city's buildings to some degree, and the historic Old Town sustained 650 hits by artillery rounds. Most reconstruction was completed between 1995 and 1999.
The Republic of Ragusa introduced a medical service in 1301, opened a pharmacy in 1317 that is still operating today, established the first quarantine hospital in 1377, abolished slave trading in 1418, and opened an orphanage in 1432. The republic also built a 20 km water supply aqueduct in 1438, designed by the Neapolitan architect Onofrio della Cava.
The walls of Dubrovnik, running almost 2 km around the Old Town and built 4 to 6 metres thick on the landward side, were used by the HBO series Game of Thrones to represent the fictional city of King's Landing from season 2 onwards. The walls drew 1.3 million visitors in 2018 and have also been used in Star Wars: The Last Jedi, filmed there in March 2016, and several other productions.