Question: "...what is this?"
Answer: A shameless cash grab.
Tusker House is a character buffet in the Africa section of Animal Kingdom. Decent food (by Disney standards) with the Fab 5 visiting tables for about $55/ adult. For a few dollars more, you can upgrade your experience to include a ticket for the reserved seating area at that evening's showing of Rivers of Light. The show rarely fills up, and is not regarded by most as the best night show, but most agree that it is worth seeing once. Personally, I would rather stand in front of the Tree of Life watching 30 minutes of awakenings, but I digress.
If you are on the dining plan and can get your lunch for the same number of credits with or without the show package, you might as well include it. If you are paying out of pocket, it used to be only about $5/person more, but still not usually worth the extra cost.
Hope this helps!