Have you ever played with blocks that have numbers on them in order? That is kind of like sequence dating! It helps figure out how old things are by putting them in the order they happened.
Let's say we find some old bones in the ground, but we don't know how old they are. By looking at the layers of soil around the bones, we can tell which layer is the oldest and which layer is the youngest. We can then figure out where the bones fit in the order of those layers, just like putting the numbered blocks in order.
Scientists use different methods to figure out the age of different layers of soil or rocks, like carbon dating or looking at the fossils in those layers. Once they know the age of one layer, they can use that information to help figure out the age of other things in that layer.
So, just like how we put the numbered blocks in order, sequence dating helps scientists put things in the order they happened, so we can understand how old they are!