A picture is worth a thousand words. While memes certainly don't cover the entirety of WWII in Europe, they provide a good summary of what happened. Use them to explain the war to people whose knowledge of history is so poor that they think WWII was fought by George Washington against Mexico.
These are the memes that summarize WWII in Europe
1. When England and France expect trench warfare, but Germany blitzes through the Ardennes
After WWI, England and France expected that the next major war would simply be a continuation of the Great War: trenches, stalemates, mustard gas, etc. France even built the "impregnable" Maginot Line on the border with Germany in anticipation of this type of fighting. So what did the Germans do? They introduced a new kind of warfare, blitkrieg or lightning war, and went around the Maginot Line in 1940. The invasion went from May 10 and ended on June 25 with the capture of Paris.
2. When Britain actually puts up stiff resistance and prevents a German invasion
Following the fall of France in 1940, Britain stood alone in Europe against the Nazis. Hitler ordered an aerial campaign against the island nation in preparation for an eventual invasion codenamed Operation Sea Lion. However, thanks to the bravery and determination of the pilots of RAF Fighter Command, the German Luftwaffe would never secure air superiority over Britain or the English Channel and Sea Lion was canceled later that year.
3. The Nazis wondering where the allies will invade Europe
With America in the war following the attack on Pearl Harbor on December 7, 1941, the allies massed their forces in England for the eventual invasion and retaking of the European continent. To ensure the success of the landings, misdirection and misinformation campaigns were conducted to convince the Germans that the invasion would take place at Calais. Fake armies were created and a dead body was even dropped on the French coast with fake plans detailing a planned invasion of Calais.
4. The Nazis when the allies land at Normandy instead of Calais
Yup, the trick worked. In fact, the allied deception campaign worked so well that when troops landed at Normandy on June 6, 1944, Hitler was convinced that it was a feint and refused to send his tank reserves to reinforce the beach defenses. As a result, the allies were able to establish a beachhead and begin the push towards Paris and eventually Berlin.
5. The allies when Operation Market Garden fails
Operation Market Garden was the allied plan to invade Germany by way of Holland in September 1944. If successful, it would have ended the war by Christmas. The largest Airborne army ever assembled dropped onto key bridges and attempted to hold them long enough for the allied tank columns to roll through. However, the plan was too ambitious and eventually failed. German resistance was stiffer than expected and the tanks never reached the paratroopers at the far end of the assault.
5. When the Airborne has to stop the German counteroffensive at the Battle of the Bulge
From December 1944 to January 1945, the Germans tried for one last push to turn the war around. They attacked through the Ardennes with masses of infantry, tanks, and aircraft in a bid to reach the port of Antwerp and cut the allied supply lines. The allied forces in the area were caught off guard and the Germans made good initial progress. Famously, the 101st Airborne Division was sent in to hold the Germans. Despite being surrounded, the paratroopers refused to surrender and the Germans were stalled. The siege was eventually broken by Patton's tanks and the last German offensive was turned back.
6. When Hitler and the Nazi high command realize the war is lost
By 1945, the allied armies were squeezing Germany from the west and east. The fall of Berlin and the Third Reich was only a matter of time, and Hitler and his followers would be tried for crimes against humanity. Rather than face man's justice, Hitler and many of his followers chose to take their own lives. Even some Nazis who were captured managed to kill themselves in prison before their trials.