Okay kiddo, you know how sometimes when you play with your toys on the sandbox, you make little marks on the sand with your fingers or toys? That's sort of like what grooves are in archaeology.
When people used to live in ancient times, they would often use tools or objects to do things like grind up grains or make pottery. These tools would leave little scratches or marks on the surface they were working on, kind of like how you make marks in the sand.
Archaeologists study these marks, or grooves, because they can tell us a lot about how people used to live. For example, if they find grooves on a rock that was used for grinding grains, they can tell what kinds of grains people were eating and how they prepared them.
It's like solving a puzzle with clues, and grooves are just one of the many clues that help archaeologists learn more about the people who lived before us.