Short answers, pulled from the story.
Alba Longa was an ancient Latin city in Central Italy, situated in the Alban Hills near Lake Albano. The ancient Romans regarded it as the founder and head of the Latin League. Its precise site has been debated since the 16th century, with Castel Gandolfo being among the most frequently proposed locations.
Roman tradition held that Romulus and Remus, the founders of Rome, came from the royal dynasty of Alba Longa. Alba Longa was itself said to have been founded by Ascanius, son of Aeneas, in 1151 BC. Rome was then treated as a colony of Alba Longa established by Romulus and Remus after they were banished at birth during a dynastic struggle.
The Roman king Tullus Hostilius ordered the destruction of Alba Longa after its leader Mettius Fufetius led the Alban army away from battle during a war against Veii and the Fidenates, abandoning Rome's forces to fight alone. Tullus executed Mettius, demolished the city, sparing only its temples, and transported the entire population to Rome.
The entire population of Alba Longa was forcibly relocated to Rome, a migration that according to tradition doubled the number of Roman citizens. The leading Alban families, including the Julii, Servilii, Quinctii, Geganii, Curiatii and Cloelii, were enrolled among the Roman patricians. The Alban immigrants settled on the Caelian Hill.
Archaeological evidence shows only a string of small Iron Age villages along the south-western shore of Lake Albano, each with its own necropolis. Classicist Tim Cornell concluded there is no evidence of a powerful state in the Alban Hills at the relevant period. The villages were still in a pre-urban phase at the time of the city's destruction and are unlikely to have founded Rome.
Alba Longa was reportedly the leading city of the Latin League, a confederation of roughly thirty cities described as its colonies. The league's conferences were held by the Ferentine spring in the valley between Albano and Marino. Annual sacrifices of a white bull to Jupiter Latiaris were made on the Alban mountain, with the flesh distributed among all the participating cities.