Sin is actually an Anglo Saxon archery word. It literally means to miss the mark on the target.
Centuries ago (this is a web site about a historical event) a group of people asked God what it would take for them to be with God. Basically God said they must be holy since God is holy. The people did not understand all that holiness entailed so they asked for more details. What resulted was a list of laws or rules that everyone had to follow.
Since God required every one of the laws to be followed all the time, it did not take long for the people to realize that no one could obey all the laws. So no one could ever be with God. As a result a series of sacrifices were instituted to cover the people's failure or sin. That is until a more permanent solution came. This solution was promised many years earlier. Christians call that prophesy.
Finally after many years the solution arrived in the form of a baby. Remarkable as the child grew and became a man, he (unlike everyone else) was able to keep all the rules and laws. At the age of thirty he began telling people about God. Even more amazingly he claimed to be God himself. For such a claim, the people tried to kill him on several occasions until they finally succeeded. That man was Jesus Christ and he died on a cross (a brutal form of execution used by the Romans).
Since Jesus was able to follow all of God's rules (laws) he deserved to be with God. If he wanted he could have given up that right for himself and given it to another person. That would have been a substitutionary death. If he was only a man he could only substitute for one other person. But since he was also God, (proved by miracles and rising from the dead) his death could pay for everyone else. So God has given us a gift we don't deserve (grace).
All we have to do is to accept (receive) that gift. By doing so we are transferring the trust for payment for all we have done wrong (our sins) to Jesus' payment on the cross. Transferring your trust to Christ involves turning to God from self (repentance) and trusting Christ to come into our lives to forgive our sins and to make us what He wants us to be. Just to agree intellectually that Jesus Christ is the Son of God and that He died on the cross for your sins is not enough. Nor is it enough to have an emotional experience. You transfer your trust by faith, as an act of the will. We can do this by praying (which is talking to God). A suggested prayer is:
"Lord Jesus, I need You. Thank You for dying on the cross for my sins. I open the door of my life and receive You as my Savior and Lord. Thank You for forgiving my sins and giving me eternal life. Take control of the throne of my life. Make me the kind of person You want me to be."
If you prayed that prayer you have started on an incredible journey. Not only will you be with God forever but you have also started a personal relationship with Him right now. We encourage you to reach out to any of the sponsoring churches. An illustration is: several logs burn brightly together; but put one outside on the cold hearth and the fire goes out. 
So it is with your relationship to other Christians. If you do not belong to a church, do not wait to be invited. Take the initiative.