what is the differnce betweem broker and webmethod trading network??

What do you mean by difference?

Broker is a messaging layer, from which different IS communicate, document publishing is done. It is used within an organization.

TN is a console for watching out the transactions between the trading partners, where you can see that if the delivery or process on the inbound/outbound transactions are done or not.

For further, check out the documentation, which will clear you out more.

Trading networks is used for exchange of documents(flatfile,xml, EDI etc…) with organization’s partners. It provides features(proc rules… TPA’s) that helps in document exchange, processing and delivery.

Broker is messaging queue that has capabilities of publishing and subscription to documents.

Refer Broker admin guide, pub/sub guide, TN user guide for details