Okay kiddo, so a long time ago in 1915 a group of people got together in a place called Zimmerwald in Switzerland. They were all very upset because there was a big war going on called World War I and they didn't like it.
These people were called socialists, which means they believed in sharing things and making sure everyone is treated fairly. They didn't like war because they thought it was bad for regular people and only helped rich and powerful people.
So, they had a big meeting to talk about what they could do to stop the war. They talked about things like how to bring peace, how to help poor people, and how to make sure everyone is treated fairly.
Lots of different people came to this meeting, from different countries and with different ideas. They talked about all these different ideas and tried to come up with a plan to make things better.
Even though they might not have been able to stop the war right away, the Zimmerwald Conference was important because it showed that people from all over the world could come together and work towards a better future for everyone.