From Bulbapedia, the community-driven Pokémon encyclopedia.
Teala is an NPC character in FireRed/LeafGreen/Emerald/Diamond/Pearl. She is the attendant on the second floor of Pokémon Centers, and she manages items that players receive via the Mystery Gift function. The first time that a player goes to the second floor of a Pokémon Center, she will explain the Wireless Communication in the Generation III games excluding Ruby/Sapphire and the Generation IV games. In Generation IV, she is located in the Pokémon Center basement and gives the player a Pal Pad the first time they go down there.