What does the parable of the lost sheep mean?

The meaning of the parable, each and every one of us are very precious in the sight of god. and he has no desire to see any one should get lost for ever.
It means that God rejoices over a sinner who repents than 99 good people who don't need to.
Here in the parable of the lost sheep, we sinful man are the lost sheep, and god is trhe sheperd who looks out for the sinners to repent and come home.
This is a story told by Jesus of Nazerus to explain his and God's love for everyone. If there is a hundred good people, but one person sins, he will leave all the others because they are doing fine, and go to comfort and save the sinner. Hope this helps on your path to God's mercy.
God will go to great lengths to be available to those who stray - He will be right there waiting when they are ready to turn to Him.