Final answer:
Relations of ideas are necessary truths known a priori, like mathematics, while matters of fact are contingent truths known through experience, like landmarks' locations. Hume attributes our knowledge of matters of fact to habitual associations formed through repeated observations.
Step-by-step explanation:
The difference between relations of ideas and matters of fact is foundational in the philosophy of David Hume. Relations of ideas are a priori and analytical; they are necessary truths that do not depend on any experience. For example, mathematical truths such as '2 + 2 = 4' are relations of ideas that can be known just by thinking about them. On the other hand, matters of fact are empirical and discovered through experience; they are contingent truths that could have been otherwise. An example of a matter of fact is that 'The Eiffel Tower is in Paris'; this is something we know through observation.
According to Hume, our knowledge of matters of fact is derived from experience, specifically from the habit or custom of associating certain experiences together. When similar conjunctions are observed to occur repetitively, we come to expect one event to follow another, though there is no necessity for this in the way relations of ideas are necessarily true.