What the different Topologies in which Replication can be configured?

Replication can be configured in any topology depending keeping in view of the complexity and the workload of the entire Replication. It can be any of the following:
 Publisher, Distributor and Subscriber on the same SQL Instance.
 Publisher and Distributor on the same SQL Instance and Subscriber on a separate Instance. Publisher, Distributor and Subscriber on individual SQL Instances.