Dimension restriction in an analytic privilege

Hi,

While reading the HANA security guide, I came across the following line. 

"Within one dimension restriction, all value filters on the corresponding dimension attribute are combined with logical OR. "

eg. Can someone explain this with an example?

"Within one Analytic Privilege, all dimension restrictions are combined with logical AND. "

eg. YEAR=2008 AND COUNTRY=US

What does a dimension in HANA mean. Is it a single field or is a attribute view in am analytic view?

I am from  a BW background. Dimensions in a BW infocube are a grouping of related fields.

Thanks,

Benedict