One butterfly means, our world will be beginning a new life.
According to Kwaidan: Stories and Studies of Strange Things, by Lafcadio Hearn, a butterfly was seen in Japan as the personification of a person's soul; whether they be living, dying, or already dead.
The ancient Greek word for "butterfly" is ψυχή (psȳchē), which primarily means "soul" or "mind".
White butterflies also symbolize past spirits/souls. I've come to believe they are signs of good luck or angels watching over you. White butterflies have many different symbolic meanings in different cultures. Some belief it is the soul of child, others believe it is a sign of death.
It is a spiritual symbol for life after death because of its metamorphosis, or transformation, from a caterpillar that crawls on the ground to a beautiful, almost ethereal creature that flies through the air. It has also become a symbol for personal growth and spiritual rebirth.It represents resurrection.
This symbolism was also used in early Christianity as a symbol of the soul.
Other cultures believed that spirits of the dead took the form of white butterflies.