Short answers, pulled from the story.
338,226 Allied soldiers were evacuated during Operation Dynamo between the 26th of May and the 4th of June 1940. On the first day only 7,669 men were rescued; by the eighth day the total had surpassed 338,000.
The halt order was issued by Generaloberst Gerd von Rundstedt on the 23rd of May 1940 and endorsed by Hitler on the 24th of May, stopping German panzer units from advancing on Dunkirk. Rundstedt was concerned about exposed flanks, overstretched supply lines, and marshy terrain unsuitable for tanks; Hitler approved the order and later endorsed the Luftwaffe finishing the job instead. The order was not rescinded until 15:30 on the 26th of May, giving Allied forces time to construct defences and begin the evacuation.
The Little Ships of Dunkirk were a flotilla of hundreds of small civilian vessels, including fishing boats, pleasure craft, yachts, Thames vessels, and motor lifeboats, called into service to ferry soldiers from the beaches out to larger ships. Many were requisitioned by agents of the Ministry of Shipping without their owners' knowledge and sailed by civilian crews due to naval personnel shortages. The first little ships arrived at Dunkirk on the 28th of May, and by the 31st of May nearly four hundred small craft were crossing the Channel voluntarily.
Operation Dynamo was planned and commanded by Vice Admiral Bertram Ramsay, operating from naval headquarters beneath Dover Castle. Planning began on the 20th of May 1940, and Ramsay managed the flow of more than 861 vessels across three routes to and from Dunkirk. On the ground at Dunkirk, Captain William Tennant served as senior naval officer, redirecting troops from the beaches to the east and west moles.
The British Expeditionary Force abandoned nearly all of its heavy equipment during the evacuation. Losses included 2,472 pieces of artillery, almost all of the 445 tanks dispatched to France, roughly 65,000 vehicles, 20,000 motorcycles, and large quantities of stores, ammunition, and fuel.
Churchill addressed the House of Commons on the 4th of June 1940, calling the evacuation "a colossal military disaster" while also describing the rescue as "a miracle of deliverance". He explicitly cautioned that "we must be very careful not to assign to this deliverance the attributes of a victory", adding that "wars are not won by evacuations".