Mousterian is a fancy word that describes a way ancient humans made tools during a time called the Middle Paleolithic period, around 300,000 to 30,000 years ago.
So, imagine you want to make a really cool toy car out of clay. First, you need to find the right kind of clay that is soft enough to shape, but not too soft that it falls apart. Then, you use your hands or some simple tools like a toothpick or a stick to shape the clay into the shape you want.
In the same way, ancient humans during the Mousterian period would find rocks or stones that were hard and strong enough to shape into tools. They would chip away at the rocks using other stones to create sharp edges and points, like a knife or a spear.
These tools allowed early humans to do all kinds of things, like hunt for food or build shelters. The Mousterian period was a really important time in human history because it was when early humans began to use more complex tools and technology to survive and thrive.