Normally you would do it like this:
http://myurl/sitename/listname/Forms/AllItems.aspx?FilterField1=Country&FilterValue1=America
This is great and you can extend it to include other columns by using FilterField2,FilterValue2,FilterField3,FilterValue3 and so on.
But what if you want to filter the same column with more than one value, using FilterField options will only allow one filter per column. So in comes "FilterName and FilterMultiValue"
To use, its simple
http://myurl/sitename/listname/Forms/AllItems.aspx?FilterName=Country&FilterMultiValue=America;South Africa
BAM! you now have a filter on the same field, its an OR filter, but its still great :)
