Acheulean is a big and fancy word that describes a really old way that people used to make tools a long, long time ago. Imagine your great-great-great-great grandparents making things out of rocks instead of toys or phones like you have today. But instead of just throwing rocks at things, they used a special way of shaping them into tools. It was kind of like carving a piece of wood, but with rock instead.
The people who made these tools lived a really long time ago, around 1.7 million years ago. They were the first ones to figure out how to make really special tools that could help them do different things, like cutting food or building a shelter. They were really good at it too, so good that some of their tools have been found all over the world!
Today, we can still see what these Acheulean tools looked like by looking at them in museums. They might not be as cool as the toys and gadgets you have now, but they were really important for helping people a long time ago survive and live better lives.