The Lotus is a common spiritual symbol in the eastern world.  In the west, it is often replaced with a lily or rose, but the meaning is essentially the same.
    The lotus, a type of water lily, is the flower of light.  It represents the cosmos rising from the waters of chaos.  It is the flower of the sun, or more specifically, the flower of the spiritual sun.   The lotus opens and closes with the sun, so represents solar power.  It also symbolizes perfection since it's flower, fruit and leaves form circles, the symbol of perfection.  More specifically, it represents spiritual perfection and the gradual process of spiritual enlightenment as the lotus opens gradually in the morning light.
    A lotus with a flame over it symbolizes divine revelation and the joining of the two forces represented by fire and water.  It many ancient cultures, the lotus was a funerary flower so is also symbolic of death and rebirth.  In yoga and similar disciplines, it represents the opening of the "third eye" or the crown chakra, although all of the chakras are sometimes depicted as lotus flowers in various colors.  
    In Buddhism, it represents the progress of the soul.  The roots are in the mud, the step in the water, while the blossom sits on the water in the sunlight.
    In Christianity, the archangel Gabriel is sometimes depicted holding water lilies, basically a western version of lotus flowers and, as in other religions, symbolizes the joining of fire and water, enlightenment, growth of the soul.
    Different colors change the symbolism of the lotus slightly.  The blue lotus symbolizes the triumph of the spiritual over the mundane (material) world.