I defined an entity Person: 

```
class Person: NSManagedObject {

@NSManaged var firstName: String
@NSManaged var lastName: String

}

```

Then: 

```
let person = NSEntityDescription.insertNewObjectForEntityForName(entityName, inManagedObjectContext: managedObjectContext!) as! Person

        person.firstName = "First name"
        person.lastName = "Last name"

```

Now I'm confused, is person an attribute like firstName and lastName? What is insertNewObjectForEntityForName?