Classes and their instances

Where do I find information, preferably with examples, on how you use Classes and Instances of those classes?

I see common pattern like ovn:Resource and ovn:ResourceType, looking at Relationship I notice

• type: "object" | why not "@type": "rdfs:Class"?
• ovn:relationshipType as I interpret it has rdfs:range ovn:RelationshipType | why not "@type" with value of some [ rdfs:subClassOf ovn:Relationship]?
• Do you use rdfs:subClassOf in your modeling at all?

I must admit just starting process of understanding your modeling so please excuse me my ignorance 👶