There were a number of major consequences of World War I. The war impacted different countries in different ways. Of course, the major human impact of the war was the fact that it killed and maimed so many people and led to so much suffering.
For Germany, the war was a disaster. It led to the loss of huge amounts of territory. It also led to national humiliation.
For France and England, the main impact of the war was that it led to an intense desire to avoid another such war. This led to things like the punishing terms of the Treaty of Versailles. It also led the French, for example, to create the Maginot Line to, they thought, prevent another German invasion. Both countries also participated in the creation of the League of Nations, which was also supposed to prevent war.
For the US, the war also led to attempts to make sure it never happened again. These included the creation of the Washington Naval Treaties to prevent arms races. The US then became isolationist, hoping never to be drawn into war again.
For the world as a whole, the main consequence of WWI was that it led to WWII. The world order created after WWI angered countries such as Germany and Japan, which then took actions that eventually led to WWII.
There are many other impacts of this war, but these are the most important in terms of the broad scope of world history.