Shachtmanism is a way of thinking about politics that began a long time ago with a man named Max Shachtman.
Imagine you're at a big party with your friends. Everyone likes to play games, but you and your best friend like different games. You like to play tag, but your friend likes to play hide and seek.
Now, let's say that this party is like the world, and everyone has different opinions and ideas about how things should be. Shachtmanism is about people who want to make changes in the way the world works, but they disagree about how to do it.
Shachtmanists believed in something called "Third Camp" socialism, which means that they didn't want to be part of either the "capitalist" or "communist" camps during the Cold War. Instead, they wanted a third way that would be different from both capitalism and communism.
So, going back to the party metaphor, imagine that there are two big groups of people playing games: the tag players and the hide and seek players. The Shachtmanists would be the smaller group of people who don't want to join either game, but want to come up with their own game that is different from both. They believe that the only way to make a real change in the world is to come up with a new way of thinking about things, rather than just choosing sides.
Does that make sense?