Sometimes we have the requirement where we need to establish communication in between two portlets for example any action done in one portlet redirecting the end user to other portlet where some kind of result is displaying as per action done on FIRST portlet. 

So in this use case we have to use liferay inter-portlet communication mechanism which serve the action performed by end user in one portlet and provide the result to the second portlet where the action result needs to be DISPLAYED. We can say that it works on striker-catcher mechanism. 

JSR style inter portlet communication ensures that your portlets are going to work on any other JSR COMPLIANT portal server. If you use a liferay specific way to communicate between portlets than you may not be able to deploy and run the same portlet war on another JSR compliant portal (e.g. Apache Pluto)

Sometimes we have the requirement where we need to establish communication in between two portlets for example any action done in one portlet redirecting the end user to other portlet where some kind of result is displaying as per action done on first portlet. 

So in this use case we have to use liferay inter-portlet communication mechanism which serve the action performed by end user in one portlet and provide the result to the second portlet where the action result needs to be displayed. We can say that it works on striker-catcher mechanism. 

JSR style inter portlet communication ensures that your portlets are going to work on any other JSR compliant portal server. If you use a liferay specific way to communicate between portlets than you may not be able to deploy and run the same portlet war on another JSR compliant portal (e.g. Apache Pluto)