When Jesus appeared to his disciples, they were in the upper room with Mary - they were afraid and lost without Jesus. They thought He had died and they were afraid of meeting a similar fate.

Jesus' greeting "Peace be to you" was significant.   Just as Spring is natures proof of new life - so too, Jesus' resurrection from the dead is a proof of the eternal life of the soul.  The message he conveyed to the disciples was that after death to earthly life there is eternal life of bliss with the Lord - Heaven.  Just as the seed has to lose its outer form to grow into a tree, so too the body has to return to dust in order that the soul may be set free to live eternally with God. I think this is what it means.