Who is Zelda to which the Legend of Zelda series refers to?

Answer 1

Zelda, Princess of Hyrule (usually shortened to Princess Zelda) rules the Kingdom of Hyrule, and has appeared in every game to date with the exception of Phantom Hourglass, however Tetra, who appears in the game instead, is the alter ego of Princess Zelda. Zelda will usually be captured by Ganon (or Ganondorf, depending on the game) or another villain, whom Link must save from Evil's clutches.

Zelda also has her own personal theme, "Zelda's lullaby".