First comes a Tutorial. It contains a large a number of screenshots, and introduces the basic controls and gameplay while following an example game. It might contain some mild spoilers. Because the placement of rooms and monsters in the dungeon is random, your games will be different, but you will still be exploring a dungeon and encountering monsters.
Next come the Spoilers. These will reveal things not in the NetHack documentation itself. Rather than being a comprehensive list of everything (all item prices, all possible potion effects, ...), the spoilers in this guide (will) present strategies for playing NetHack well.