This is an agent-based model. That means agents individually decide whether to do an action. We then study patterns that appear in aggregate.
This is a model of segregation. There are two agent "identities."
Agents live on a straight line. And they look to their left and right to determine how many share the same identity. If this falls below their preference for homogeneity, they are unhappy.
When they are unhappy, they survey empty plots of land along this straight line, and move to one where they would be happy.
The main consistent result of the model is that, when people move, they contribute to a level of homogeneity in the aggregate that is higher than their aggregate preference for homogeneity.