Could anyone please explain the difference between application and integration service in IIB. I have referred through documentation but it was not clear. For example, if I have to create a service based on wsdl which has some 3 operations.Should I create it as integration service or application.Please suggest
So with an Application it's roll your own in that you have to build everything.
With an Integration Service you can import a WSDL and the framework of your flow will be generated for you.
So if you are being given WSDL's for the services you want to build then using an IS may be the way to go.
Personally I don't like some of the aspects of the generated code but that's me. I'm currently working on a project that uses REST API's and am using the REST API project option for my projects and it generates code.