A proxy allows to channel your internet access through a specific host. It can be useful to proxy through the ist service. That way, you can browse the web as if you were browsing within the ist intranet. This provides you access to registered libraries online etc...
Basically, from outside the IST, you'll need to configure your proxy settings in your browser with
Then simply provide your fenix istxxxxxx login. Note: you must own a fenix login in order to authenticate in the ist proxy services.