This essay by Gottlob Frege (1848-1925) was published in 1892 in the journal Zeitschrift für Philosophie und philosophische Kritik, pp. 25-50. Dealing with the “philosophy of language,” it discusses the distinction that should be made between the sense and reference (hence: the title of the essay) of linguistic expressions.
It will be helpful to have the essay in hand to follow our discussion with maximum profit. It is available in more than one English-translation editions. Our discussion here covers the pages corresponding to pp. 25-31 of the original.