If you don't mind Sara, I'll let Wolfchan answer this because I think she understands more about this than I do.

The basics, as I understand them, are that the pagan traditions has holidays at similar times of year to the Christian holidays Christmas and Easter (I think they are the Winter Solstice and Spring Equinox) and in the pagan tradition the Winter Solstice is associated with decorated trees and the Spring Equinox with eggs as signs of new life. So those symbols, trees and eggs, are shared by both faiths.

Does that explanation make any sense?