From Bulbapedia, the community-driven Pokémon encyclopedia.
A Pokémon journey is a quest undertaken by a Pokémon Trainer to learn to live and work with Pokémon. In the anime, a person's Pokémon journey can begin as early as the age of 10, when they can first legally apply for a Pokémon Trainer's license. It is at this point that a Pokémon Professor can give them a starter Pokémon native to their own region, though many people befriend or are given other Pokémon prior to being legally able to be Trainers.
Pokémon journeys have many different possibilities, with some Trainers choosing to gather a region's Badges from its Pokémon Gyms, their ultimate goal being the Pokémon League. Other Trainers instead choose to become Coordinators, gathering Ribbons by competing in Pokémon Contests with the goal of winning the Grand Festival to become a Top Coordinator. Some other Trainers may choose to become Performers and compete in Pokémon Showcases with the goal of being the Kalos Queen. Others journey in order to learn about and be proficient about certain types of Pokémon while some may choose to journey to pursue certain occupations like Pokémon breeding, Pokémon watching, and Pokémon styling. Regardless of the reason behind the journey, Trainers must learn to work in all sorts of circumstances to become the best in their field.
Pokémon Trainers may choose to journey alone or with friends and people they meet along the way. On their journey, Trainers can stay at a Pokémon Center free of charge, where their Pokémon can be healed by the resident nurse.
In the games
The core series games chronicle the Pokémon journey of an individual Trainer, the player, across a region that is dependent on the game being played. This journey is typically focused on defeating the region's eight Pokémon Gyms, defeating the Elite Four, and becoming the Champion, though there are often sidequests along the way. A villainous team will always show up during the journey to impede the player's progress, and often, after the Pokémon League has been conquered, several post-League areas are available to continue the journey.
While sending children alone on a Pokémon journey is a normal part of life in the Pokémon world, many mothers remain understandably hesitant at letting their children grow up.
In the anime
Ash, ready to go on a new journey
The anime follows the Pokémon journey of Ash Ketchum, who started off with his first Pokémon, a Pikachu, in the first episode, and as of this point has journeyed across several regions, competing in each of their Pokémon Leagues. His ultimate goal is to become a Pokémon Master, while he is joined by his friends along the way, each with their own goals.
The anime established that children may go on on a journey only at or after the age of 10 as this is the age they obtain their Pokémon Trainer's license. However, many children below the age of ten have been shown to own Pokémon in the anime, a notable example being Iris and the ownership of her Drilbur.
A Pokémon journey in the anime is considered to be a rite of passage and many viewpoints have sprouted about Pokémon journeys throughout the course of the anime. Ash's mother has little misgivings about letting him go; her own husband, Ash's father, is in fact still on his own Pokémon journey. Other adults, such as Silver, are also still traveling with their Pokémon, and several adult Trainers, such as Cynthia, have attained a status that allows them to remain in one place rather than traveling. Other adults, however, such as Mandy, see an adult on a Pokémon journey to be somewhat immature, preferring that they settle down instead.
In the manga
In the Pokémon Adventures manga
Pokémon Adventures follows the journeys of its protagonists in each of their self-named chapters: Red, Blue, and Green star in the Red, Green & Blue chapter, Yellow stars in the Yellow chapter, Gold, Silver, and Crystal star in the Gold, Silver & Crystal chapter, Ruby and Sapphire star in the Ruby & Sapphire chapter, and are joined by Emerald in the Emerald chapter with Gold and Crystal also join in later on, Red, Blue, Green, Yellow, and Silver return to the forefront in the FireRed & LeafGreen chapter, Diamond, Pearl, and Platinum star in the Diamond & Pearl chapter, later mainly going separate paths in the Platinum chapter, Gold, Silver, and Crystal star again in the HeartGold & SoulSilver chapter, and Black and White star in the Black & White chapter.
In other languages