Okay kiddo, so a long time ago in the United States, workers realized that if they band together and form a group called a union, they can ask their boss for better pay, safer working conditions and other fair things.
But, some bosses did not like that because they did not want to spend more money or lose control over their workers. These bosses started doing things to stop unions, this is called union busting.
One way bosses did this was by hiring people to spy on union meetings and then fire the workers who attended them. Another way was to bring in new workers to replace union workers who went on strike, which means refusing to work until the boss agrees to listen to the workers' demands.
Some bosses even used violence like hiring armed guards to attack workers or have police arrest them. This made it really hard for workers to form unions and to make their working conditions better.
Over time, workers kept fighting for their rights and the government made laws that protect workers' rights to form unions and to fight against union busting. But, there are still many workers today who continue to face union busting from their bosses.