It comprises ten randomly generated, progressively more complex areas, each with a number of Trainers. Each area contains a gate Trainer and a Boss Trainer. Defeating the gate Trainer of an area unlocks the area's Boss Trainer room, while defeating an area's Boss Trainer allows the player to challenge the next area. Other Trainers in each area may also be challenged. A Nurse on each floor will heal the player's Pokémon after being defeated in battle, but only once. Some rooms will contain various puzzles allowing for players to use moves such as Strength to more easily maneuver the room. Unlike true battle facilities, the player will earn experience and money in battles. The player will forfeit the money earned during a challenge if the player loses or retires.
The Trainers in each area have a randomly selected team of two Pokémon from a personalized pool of about nine Pokémon. The Boss Trainer of each area has three Pokémon, which are fixed for each battle. The levels increase as the player progresses through the areas, with vast level differences between the first and the tenth area. The Boss Trainers' Pokémon have slightly higher levels than those of other Trainers in the area, and they will be holding a wider variety of items, including Black Sludge, Focus Sash, Life Orb, or Gems.
Starting from Area 6, the areas are separated into different floors, which the player has to explore in order to find the gate Trainer and/or the Boss Trainer. Each floor has its own set of rooms, Trainers, and Nurse.
Pokémon seen by the player while battling within the White Treehollow do not contribute to Pokémon seen in the player's Pokédex.
Upon defeating the Boss Trainer of an area, the player is rewarded with one or two items within a selection, as presented below. As can be observed, players are rewarded much less for completing Areas 6-9 (and arguably 10) than they are for completing Areas 1-5, although the former have higher difficulty and require much more time to complete.
In addition, players of White 2 will also receive the Treehollow key to send to Black 2 players upon completing Area 5 for the first time.
The Boss Trainers always use their same set of three Pokémon. Benga is the Boss Trainer of Area 10 in White 2, and upon first visit in Black 2. Players of Black 2 will face Jariel instead of Benga on subsequent visits. Each Boss Trainer has their Pokémon with 3 levels more and gives the player 600 more than the previous area's Boss Trainer.
Although the White Treehollow disables the Bag menu in and outside of battle, making players unable to use healing items such as Hyper Potions or Full Restores, players are able to heal their Pokémon by using HP-restoring Pass Powers, and can utilize the Pokémon menu to make their Pokémon hold any item, including those with in-battle healing/curing effects.