Proto-industrialization was a time a long, long time ago when people didn't have machines to help them make things. Instead, they used their hands and simple tools to make things like clothes or furniture. People made these things in their homes with their families and neighbors.
But, something interesting happened. Some people started to specialize in making just one thing, like a certain type of cloth. They got really good at it and could make more of it than they needed just for their family. Then, they started to sell it to other people in their town or even in other towns.
This is called proto-industrialization because it was the beginning of people making things on a larger scale, but they didn't have factories like we do today. They still made things in their homes, but they started to specialize and sell their products to other people.
This led to more trade happening between towns and even countries. People didn't have to make everything they needed themselves. They could buy things from other people who were really good at making them. This made life a little easier and helped to create a more complex economy.