Starter Pokémon, or Starters, are the Pokémon a trainer chooses at the beginning of their Pokémon journey.
In each generation of Pokémon games, a set of Starter Pokémon are available for new trainers to choose from in sets of three; the types that make up these sets are Fire, Grass, and Water. However, Pokémon Yellow is currently the sole exception to all the above, with Pikachu as the only starter available to the player.
In Unova, the Starters, with the exception of Tepig, Pignite and Emboar, originally had signature attacks, but were also given to certain other Pokémon: Snivy possesses Leaf Tornado, Oshawott possesses Razor Shell and Tepig alone possesses Heat Crash.
All Starter Pokemon have Hidden Abilities, such as Greninja with Protean.
Except for Pikachu and Eevee, all the Starters final evolutions can learn the ultimate attacks by move tutor upon reaching maximum happiness. Venusaur, Meganium, Sceptile, Torterra, Serperior, Chesnaught, and Decidueye can learn the ultimate Grass attack Frenzy Plant. Charizard, Typhlosion, Blaziken, Infernape, Emboar, Delphox, and Incineroar can learn the ultimate Fire attack Blast Burn. And Blastoise, Feraligatr, Swampert, Empoleon, Samurott, Greninja and Primarina can learn the ultimate Water attack Hydro Cannon.
However, both Eevee and Pikachu can learn what can be called the ultimate attacks in there respective type in any form. Pikachu can learn Volt Tackle, and Eevee in any of its evolved forms, can learn Hyper Beam.
The starters also have the Pledge moves that are exculsive to them: Bulbasaur, Chikorita, Treecko, Turtwig, Snivy, Chespin and Rowlet have Grass Pledge, Charmander, Cyndaquil, Torchic, Chimchar, Tepig, Fennekin and Litten have Fire Pledge and Squirtle, Totodile, Mudkip, Piplup, Oshawott, Froakie and Popplio have Water Pledge.
The Eevee in XD can evolve five different ways by the player's choice, two of which are types starter Pokemon typically are; the Grass-type Eeveelution wasn't introduced until the following Generation.
Pikachu is the only Starter that has a pre-evolution.
The rival trainer the player character comes across will always pick the player's Pokémon's weakness, with a few exceptions.
Thus far, all Fire-type starters have a flame somewhere on their bodies by their final evolution. Three of them, Charmander, Cyndaquil, and Chimchar, have such a flame from the beginning.
Cyndaquil is the only one of them that can disengage it at will, and the only one of the three not to have it on the tail (Chimchar's relocates to the head in its final evolution).
In the first six Generations the vast majority of fully evolved Fire type starters end up dual-type with Typhlosion being the sole exception, however three out of six Grass type starters and three out of six Water type starters never end up dual-typed.
Sceptile gains Dragon as a secondary type on Mega Evolving, the only Mega Evolved starter to gain a new type (Charizard was already dual when the Mega X version replaces Flying with Dragon).
Starting in Generation III with Ruby/Sapphire/Emerald the starters began to be obtained outside the resident professor's lab with Hoenn having the player character save Professor Birch from a wild Pokémon by picking from Treecko/Torchic/Mudkip in his briefcase, the wild Pokémon was a Poochyena in Ruby/Sapphire and a Zigzagoon in Emerald. For Generation IV in Diamond/Pearl the Player and their rival find Sinnoh's starters Turtwig/Chimchar/Piplup inside a briefcase left behind at Lake Verity's shore by Professor Rowan, though in Platinum Dawn/Lucas returns it to Rowan shortly after he stops them from walking into the tall grass just outside Twinleaf Town giving them out on the spot. In Black/White Professor Juniper delivers a present to the player character's house containing the starters Snivy/Tepig/Oshawott. Black 2/White 2 had Bianca giving them to the player character in Aspertia City, their home town, from inside a container. In Kalos the player character receives one of the regional starters, Chespin/Fennekin/Froakie, from a kid named Tierno in Aquacorde Town at an outdoor table along with several other kids, and they also get a Kanto starter from Professor Sycamore. In Sun and Moon, the player recieves their starter, Rowlet, Litten, or Popplio, from Kahuna Hala after saving Nebby from Spearow. In Ultra Sun and Ultra Moon, the player recieves their starter from Professor Kukui after being ambushed by a Yungoos on Route 1.
In Omega Ruby/Alpha Sapphire, Professor Birch will give Torchic/Treecko/Mudkip to save him from the wild Pokémon. After beating the Elite Four and the Delta Episode, he will give the choice of Chikorita/Totodile/Cyndaquil to rescue him again. After beating the Elite four a second time he will give the choice Turtwig/Piplup/Chimchar. Now beating the Elite Four for the third time, he will give the choice of Snivy/Oshawott/Tepig. That means the player gets one of the three regional Pokémon for Hoenn, Johto, Sinnoh and Unova before they beat the Elite Four four times.
In Pokémon X and Y, two starters can be obtained. The player can pick between Chespin, Fennekin, and Froakie, then later they can choose all of the Kanto Starters except Pikachu and Eevee.
The player can later catch the first evolved forms of both the Kanto and Kalos starters in some Grass, Fire, and Water Friend Safaris. This marks the first time any Pokemon related to starters have been available to catch in the wild.
In Pokemon Sun and Moon, some Starters and their evolutions can be found through Island Scan. These include Chikorita, Cyndaquil, Totodile, Serperior, Samurott, and Emboar. This feature is expounded on in Ultra Sun and Ultra Moon, where Bulbasaur, Charmander, Squirtle, Grovyle, Combusken, Marshtomp, Grotle, Monferno, Prinplup, Chesnaught, Greninja, and Delphox are all available through Island Scan.