Proxy adapter in sap po 7.5 or 7.4 single stack.

Hey, can anyone explain about proxy adapter in single stack 7.4 or 7.5? I know the proxy configuration for single stack. I want to know about how to generate proxy object in ECC and why we are generating it. How to test proxy scenario like file to proxy and proxy to file scenarios. Your every suggestion and answer is much appreciated. Thanks.