A central distributor is used when you want to utilize a single central server to distribute all of your publications. This topology is not commonly used due to the single point of failure in the distribution server. It is also very difficult to maintain since a failure in the replication process between two servers can disrupt all servers participating in replication even if the servers are unrelated.

Central Distrbutor

Central publisher with remote distributor

In central publishing, the distributor or distribution database resides on the same server as the publisher. This topology separates the distribution database onto another server.