PeopleSoft Integration Broker is an XML messaging hub that provides system-to-system interoperability via standard web services. It can surface on any of the PeopleSoft Integration Points as XML documents over HTPP using SOAP and WSDL. This standardized approach simplifies point-to-point interoperability between systems in your enterprise or serves as the perfect gateway to the eXtended process integration (XPI) server for more complex integrations.

Gateways are essetially a pathway out of the system. There is always a LOCAL gateway in PeopleSoft which refers to the source PeopleSoft system. Other gateways may exist - for example when there are differences between PeopleTools versions.

Domains refer to PeopleSoft application server (tuxedo) domains.

Nodes define what application a message belongs to - any system that integration broker can talk to (including the local system) will have a node.

Messages define the structure of the XML sent between nodes. The key difference between asynchronous and synchronous messages is acknowledgement - synchronous messages need to be acknowledge by the receiver, aynychronous ones don't. Synchronous messages aren't used much in PeopleSoft, but I believe their main purpose is for reliability.

Queues are used to manage and group messages so that all messages are sent through the multiple pipes. Queues are used for administration of integration broker to avoid stopping everything when something is wrong. For example you can pause a one queue for messages to the report architecture without say stopping messages to the finance system.

Service Operations bring together messages, queues, handlers and routings. They essentially define how the message moves between systems.

Services seem to be used to group service operations.

Routings are used to link a service operation to a node, and can also specify transformation of a message.

Handlers contain code and logic for sending/receiving/manipulating mesages.