One of the most obvious similarities is the scale of the conflicts. Both world wars involved multiple countries and millions of soldiers, and resulted in widespread destruction and loss of life. World War 2, however, was much larger in terms of the number of countries involved and the number of casualties, with estimates of total deaths ranging from 70 to 85 million.
Another similarity is the use of new and more advanced weapons and technology. In World War 1, tanks, airplanes, and chemical weapons were used for the first time. In World War 2, these weapons were further developed and used more extensively, and there was also the introduction of nuclear weapons, which had a devastating impact on the cities of Hiroshima and Nagasaki in Japan.
Both wars also had significant political, economic, and social consequences. World War 1 led to the collapse of several European empires, the Russian Revolution, and the establishment of the League of Nations. World War 2 led to the defeat of Nazi Germany and the Empire of Japan, the Cold War, and the decolonization of much of Africa and Asia.
However, there are also several key differences between the two wars. One difference is the nature of the alliances. In World War 1, the main combatants were the Triple Entente (Britain, France, and Russia) and the Central Powers (Germany, Austria-Hungary, and the Ottoman Empire). In World War 2, the main combatants were the Allies (Britain, France, the United States, and the Soviet Union) and the Axis Powers (Germany, Italy, and Japan).
Another difference is the impact of the wars on civilian populations. While World War 1 saw extensive fighting on the Western Front in Europe and the Eastern Front in Russia, the civilian populations of these countries were largely unaffected. In World War 2, however, the war had a much greater impact on civilians, with major campaigns in Europe, North Africa, and the Asia-Pacific region, and the deliberate targeting of civilians by the Nazis and the Japanese.
Finally, the two wars had different legacies. World War 1 is often seen as a tragedy that resulted from a complex web of alliances and rivalries, and the Treaty of Versailles is often blamed for the rise of Nazism in Germany. World War 2, on the other hand, is often seen as a more clear-cut conflict between good and evil, and the war's legacy includes the formation of the United Nations, the establishment of the modern state of Israel, and the beginning of the Cold War.
In conclusion, World War 1 and World War 2 were both major global conflicts that had significant impacts on the world. While there are several similarities between the two wars, there are also several key differences that make each war unique.