Short answers, pulled from the story.
Greek fire was an incendiary weapon system used by the Byzantine Empire from the seventh to the fourteenth centuries. Its defining characteristic was its ability to burn on water, making it an effective naval weapon against enemy fleets.
The development of Greek fire proper is ascribed by the chronicler Theophanes the Confessor to Kallinikos, a Jewish architect from Heliopolis in Syria. This event occurred around the year 674 when the Muslim conquests had overrun Syria, Palestine, and Egypt.
The chief method of deployment of Greek fire was its projection through a tube known as a siphon for use aboard ships or in sieges. Portable projectors called cheirosiphones were also invented, and siphons were installed on the prow, amidships, and astern of dromon ships.
Most modern scholars agree that Greek fire was based on either crude or refined petroleum mixed with resins. The substance burned on water and could be extinguished only by a few substances such as sand, strong vinegar, or old urine.
Greek fire continued to be mentioned during the 12th century, but no report confirms its use during the 1203 siege of Constantinople by the Fourth Crusade. The weapon likely fell out of use because the Byzantines lost access to the areas where the primary ingredients were found or the secret was lost over time.