I'am a new to ontologies and Protege and I sometimes meet such words as "pun" or "punning". However, I do not have a clue what they mean. Can you clarify it for me?
"Punning" is not something that comes from Protégé but it's a feature of the Web Ontology Language OWL 2 DL, which Protégé is an editor for. "Punning" refers to the possibility of naming terms of different natures with the same IRI. For instance, you can use the same IRI for a class and for an instance, for a property and an instance, or for a class and a property. In OWL 2 DL, the context always makes it clear whether the IRI is used as a class, a property or an instance. See Section 2.4.1 of OWL 2 New Features and Rationale.