Aqua is one of the main protagonists of Kingdom Hearts Birth by Sleep. From the view of the story, it is revealed she is one of the Keyblade Wielders before Sora. Like Terra and Ventus, it is her dream to become a Keyblade Master, a dream she is the only of the three to accomplish.
Her name is Latin for "Water", while Kairi's name in Japanese means "Sea". The only connection between the two is that Aqua met Kairi in Radiant Garden in Kingdom Hearts Birth by Sleep and put a protective spell on her necklace, which later brought Kairi to Destiny Islands. Kairi, by accidentally touching Aqua's Keyblade during this time, also inherited the Keyblade from Aqua.
A Fanlisting is a place where fans of a subject gather to show their love, admiration, or such feeling, about a character, or sometime others thing such as a game, a country or even clothes. Here, the subject is obviously none other than the character Aqua from the Kingdom Hearts serie.