Short answers, pulled from the story.
The Casablanca Conference, codenamed SYMBOL, was held in Casablanca, French Morocco, from the 14th to the 24th of January 1943. It brought together US President Franklin Roosevelt and British Prime Minister Winston Churchill with their military staffs to plan the Allied strategy for the next phase of World War II.
The Casablanca Declaration demanded the unconditional surrender of Germany, Italy, and Japan. Roosevelt borrowed the phrase from Civil War General Ulysses S. Grant and announced it at the concluding press conference on the 24th of January 1943.
Joseph Stalin declined to attend, citing the ongoing Battle of Stalingrad as requiring his presence in Moscow. He was kept informed of the conference agenda and resulting agreements.
Churchill argued that a cross-Channel invasion in 1943 would result in very high Allied casualties and was not yet feasible. He preferred invading Sicily and Italy first, to draw German reserves into a theater where they could not be easily redeployed, and to give the Red Army more time to weaken Germany on the Eastern Front.
The conference called for joint leadership of the Free French forces by Charles de Gaulle and Henri Giraud. Their relationship was tense; they exchanged only formalities and had to pose twice for photographers after their reluctant handshake. Roosevelt described the meeting as a "shotgun wedding" and eventually recognized de Gaulle as the sole head of the Free French in October 1944.
The conference approved a US Navy plan to advance on Japan through the central Pacific and the Philippines, authorizing the island-hopping campaign. The source material notes that this decision shortened the Pacific War.