Ceptor Dispatcher is a Reverse Proxy Server, which is typically deployed in a DMZ zone.
It is capable of running in a servlet container of your choice, or it can run in the Web Server provided by Asseco as part of the distribution.
It has similar functionality as the Ceptor Gateway, but is based upon older technology and uses blocking IO for its communication - this means that it is unable to support WebSockets, and it takes up a running thread also while waiting for requests from backends.
That being said, it is extremely stable, and has proven its worth for the last 15+ years in highly secure and performance-critical systems.
But, newer deployments should use Ceptor Gateway instead of the Dispatcher, since it contains more funtionality, and is easier to configure. Also, new features will be added to the gateway, but in general not to the dispatcher.