I wonder about individual.

hi!

 

I am learning OWL.
I am concerned about the syntax of OWL. 

 

When individual is declared as ,
I regard the individual as a unique thing in the ontology. Don't you?

 

Is there any need owl:sameAs and owl:differentFrom?
So then, why need them? I can't understand.

 

Please explain it more clearly.
In additional, please explain difference between rdf:resource and rdf:about.
I want more material of OWL individuals.

 

Thanks.