A sharepoint Inter-Farm means that a SharePoint Farm with its own SSP [Shared Service Provider] will share the SSP to other Farms. The other farm will consume the shared SSP, which allows the reduction of duplicate services. Please refer to the following http://technet.microsoft.com/en-us/library/cc262179.aspx
To provide a quick guide you can try the following;
On the parent farm where you would like to share the SSP:
In Central Administration > Application Management > Grant or configure shared services between farms, select “This farm will provide shared services to other farms”
On the child farm where you would like the farm to consume the SSP
In Cental Admin > Application Management, Grant or configure shared services between farms, select “This farm will consume shared services from another farm”
Then it will take some time for the Parents SSP to show up in the child farm, but it is a pretty straight forward process.
Happy Playing! 
bobbyhabib