Named entities are first and foremost content objects contained in the datasource.
Named entity linking is the process of detecting entities in user utterances.
Not all utterances directly name the entities they refer to. For example, utterances like "What color does this have?" or "Show me the first one" use the expressions "this" and "the first one" to refer to an object that should be obvious from the context. In order to properly understand such expressions, the named entity linking component resolves them to contextually relevant entities.