Okay, imagine a factory is a big toy box, with lots of cool toys inside. Some people, called workers, go to the toy box every day to play with the toys and make some really cool things. They do things like putting different toys together, painting them, and making them look nice.
But sometimes, the people who own the toy box aren't very nice to the workers. Maybe they don't give them enough toys to play with, or they don't pay them enough for all their hard work. When this happens, the workers might decide to do something called occupying the toy box.
This means that they take control of the toy box and don't let the owners come in anymore. They keep playing with the toys and making cool things, but now they make the rules and they all work together to make things fair for everyone. This can be a scary and hard thing to do, but sometimes it's the only way for the workers to get what they deserve.
So occupation of factories is when workers take control of a factory to make things better for themselves and others who work there. They do this by working together and making sure everyone is treated fairly.