Single-origin chocolate means that the beans were grown in one place. If you think of chocolate as similar to wine, using beans from one place is like making wine with grapes from one vineyard or region. The benefit of single-origin chocolate is that you can taste very specific flavors—perhaps red berries, citrus, or nuts—that may not be as evident when beans from different regions are blended together.
Single-origin chocolate bars are a great way to experience the inherent flavor profiles of cacao beans from different regions. The subtle flavors of the varietals, terroir, and post-harvest techniques come across when you taste single-origin chocolates side by side. You can break bars into small pieces, and taste, smell, and breathe in the various subtleties. This may be the best way to find which flavors in chocolate (and which chocolate-growing regions) most appeal to you.