From Bulbapedia, the community-driven Pokémon encyclopedia.
Ginseng is an item in the Pokémon Mystery Dungeon series. It is a drink that boosts the power of the selected move, sometimes significantly. This effect works only for the team leader and won't affect certain kinds of non damaging moves. It also slightly fills the user's belly. It can be obtained by clearing team mazes and each of the type-based mazes in Makuhita Dojo in Red Rescue and Blue Rescue or as an occaisional reward in some rescues in Pokémon Mystery Dungeon: Explorers of Time, Explorers of Darkness and Explorers of Sky.
It can be sold for 600 Poké at the Kecleon Shop.