As you'd expect, there's plenty of helpful narration, historical photos and artwork in Discovery Tour. You also don't have to worry about getting killed, so you're free to explore as much as you want. The developers brought in Egyptologists to craft 75 guided tours, which cover things like the city of Alexandria, daily life of Egyptians, the Great Pyramids and the Sphinx.
You can jump right in to tours from the game's menu and map, and they usually involve following a golden path to various checkpoints. During a brief demo, I learned how Alexandria was founded, and why its location along the Nile delta was particularly strategic. I was surprised to discover a few things I didn't come across in school, even though I spent a few years studying ancient history. I also encountered a few photos and diagrams I hadn't seen before, showing modern excavations and illustrations of what the city might have looked like.
Discovery Tour lets you choose from several models in the game as your avatar. I enjoyed exploring Egypt as Cleopatra, but you can also choose from Julius Caesar, the main characters of the game and a host of side characters. It was strange seeing Assassin's Creed Origins in another light, after spending dozens of hours in the game murdering scores of Roman soldiers, hunting Egyptian wildlife and serving as the sword for a deposed Cleopatra. But, it made me appreciate the game all the more.