From Bulbapedia, the community-driven Pokémon encyclopedia.
Ranger Depots are small buildings featured in Pokémon Ranger: Shadows of Almia. Their main purpose is to act like a Pokémon Center for a Pokémon Ranger, providing a Save Machine and an Operator, who will recharge the Styler to full energy when asked. As seen in the picture, Ranger Depots are colored blue, and they are covered on top with grass. Their design is similar to that of a Ranger Base, however their only inhabitants are Operators. Ranger Depots are smaller than Ranger Bases, probably because of this factor. Ranger Depots do not serve any other purposes in the game other than acting as these resting points.
Players do not have to utilize Ranger Depots to advance in the storyline. Save Machines can usually be found close by, along with a Pokémon with the Recharge Field Move.
When the player first arrives in Pueltown, Luana, who is accompanying them, explains the Ranger Depot to them. She recommends that the player utilizes it in the Mission that the two came to Pueltown for. However, it is not required that the player uses it, as there are two other Save Machines and plenty of Magnemite scattered about Pueltown.
Ranger Depots are placed in convenient locations in terms of nearby Missions. They can be found in Pueltown, Boyleland, Shiver Camp and Haruba Village, and they are encountered in that order. Ranger Depots can be especially helpful when the player is partaking in the Missions "Get the Blue Gem!", "Get the Red Gem!", and "Get the Yellow Gem!", as the Depots can be found in the closest civilization to where the Missions take place.