Answer:
   
   This is just a custom. The halacha is that one should cover one's eyes
   before lighting. Why? The blessing for a mitzvah is supposed to
   preceed the mitzvah. However, you can't make the blessing on lighting
   Shabbat candles before lighting , for once you make the blessing it's
   Shabbat, and you are no longer allowed to light the candles. So, you
   cover your eyes so that you start /using/ the light only after the
   blessing.
   
   Waving your hands three times beforehand is a kabbalistically derived
   custom. According to the Zohar, the human soul has five levels: three
   are internal and comprise your individual self [the power to live
   (nefesh); the mind/will (ru'ach), and the spirit (neshamah)]; two are
   external and refer to things outside your self (chayah (from the word
   "alive") and yechidah (singular)). This custom involves the internal
   aspects of the soul. To accept Shabbos into one's entire self, one
   needs to prepare body, mind, and soul--nefesh, ru'ach and neshamah.
   With each wave of the hands, one should consciously take a deep breath
   and try to feel the atmosphere of Shabbos touching another aspect of
   your being.