Short answers, pulled from the story.
The British officially recognise the Battle of Britain as lasting from the 10th of July to the 31st of October 1940. German historians regard it as a single campaign lasting from July 1940 to May 1941, including the sustained night bombing known as the Blitz.
The name comes from a speech Winston Churchill delivered to the House of Commons on the 18th of June 1940, in which he said: "What General Weygand called the 'Battle of France' is over. I expect that the Battle of Britain is about to begin." The speech was given more than three weeks before the battle's officially recognised start date.
The RAF could muster approximately 1,103 fighter pilots on the 1st of July 1940. About 20 percent of all pilots who took part were from non-British countries; the RAF roll of honour lists 595 non-British pilots, including 145 Poles, 127 New Zealanders, 112 Canadians, and 88 Czechoslovaks.
The Dowding system was an integrated command-and-control network that linked Chain Home radar stations and Observer Corps reports to Fighter Command Headquarters at Bentley Priory, then to Group and Sector controllers who directed RAF fighters to intercept incoming raids. It raised the average interception success rate from roughly 30 percent to above 75 percent during the battle.
The Luftwaffe failed to destroy RAF Fighter Command because of poor intelligence, inconsistent strategy, and the effectiveness of the Dowding system. German commanders consistently believed they were attriting the RAF at three times the actual rate, and shifted targets repeatedly rather than concentrating on a single objective. The Bf 109's limited range of 600 km also meant German fighters had barely enough fuel to escort bombers over southern England.
The No. 303 Polish Fighter Squadron became the highest-scoring fighter squadron of the Battle of Britain, despite joining the fighting two months after the battle began. Air Chief Marshal Hugh Dowding wrote that without the Polish squadrons and their gallantry, he hesitated to say the outcome of the battle would have been the same.