What were the changes in warfare and weapons between World War 1 and 2 ?

World War I was dominated by the machine gun and the artillery piece. Machine guns made it possible for men in trenches to defend themselves against enormous numbers of attacking infantry. There was no other way to attack than to bunch all the men together and charge with rifle and bayonett right at the trench, which usually resulted in the attackers being mowed down in great numbers. The weapons and tactics favored the defensive and so the war was very largely static with both armies occupying long long systems of trenches that cut all the way across France and Belgium. There was virtually no movement for years. Tens of thousands of men might be killed just trying to gain a few yards of ground.

Between the wars great advances were made in tanks and airplanes. These vehicles could go much farther and much faster than a walking infantry man and they were armored and carried heavy guns. This made trenches and other fixed fortifications obsolete. The tanks could simply go around them and attack in the rear. Thus World War II was a war of incredibly fast maneuvering. The Germans coined the term "blitzkrieg", or lightning war, to describe it.

Lot of myths being propagated here. WWI actually saw repeated campaigns of movement, particularly on the Eastern Front. In contrast, WWII certainly had periods of stalemate and even trench warfare.

WWII saw many technological advances which had a profound effect on tactics and strategy. In particular, radar, radios, and sonar had significant impacts. The advent of the aircraft carrier and the improvements made to submarines and torpedoes significantly changed the shape of naval warfare. The tank and other armored vehicles saw armies become more mechanized and mobile, leading to a high degree of operational manuever warfare. The Germans didn't coin the term "blitzkrieg" (this was coined by the Western press) and it is rarely found in any of their publications of the time period. They were proponents of Bewegungskrieg, the "war of movement". They sought to avoid Stellungskrieg, or the "war of position".

Airpower also became highly developed and deployed on both the tactical and strategic levels. It had a far greater impact on the fighting than it did during WWI.

It would take many pages to fully answer the question, but this gives you a quick, general idea.