ORM tools evaluation features

I am doing evaluation of different Data access layer code generating tools for dotnet.

Many people in the industry do evaluation of t he tools based of many points.3 of those points are not understandable to me.

1. Maintains single identities for objects returned from queries

2.Resolves Circular Identities

3.Business rule Support

Can somebody please help me in understanding in laymans language what these means

Cheers

leo