The meanings for the Sun are fairly simple and consistent.
Young, healthy, new, fresh. The brain is working, things that were muddled come clear, everything falls into place, and everything seems to go your way.
The Sun is ruled by the Sun, of course. This is the light that comes after the long dark night, Apollo to the Moon's Diana. A positive card, it promises you your day in the sun. Glory, gain, triumph, pleasure, truth, success. As the moon symbolized inspiration from the unconscious, from dreams, this card symbolizes discoveries made fully consciousness and wide awake. You have an understanding and enjoyment of science and math, beautifully constructed music, carefully reasoned philosophy. It is a card of intellect, clarity of mind, and feelings of youthful energy.