Sin is living out of relationship with God, not living according to God's will, and thus transgressing His will in thought, word an deed.
People cannot save themselves by their good works or restore themselves to a right relationship with God.
God sent His Son, Jesus, into the world. He is both true God and true man. He lived to fulfill God's law for us, died on the cross to pay the penalty our sins deserved, and rose from the dead so that we might have eternal life.
Because of Jesus' death on the cross, God declares a human being just - or righteous - and forgiven. This happens not because of human effort, but because the justification won by Jesus is applied to the one who believes in Jesus as Savior.
Faith in Jesus is a gift of God, given by the power of the Holy Spirit, thus all the glory belongs to God.
The means of grace are the word, Holy Baptism, and Holy Communion. By these means, God applies the merits of Jesus' atoning death to all who believe in Jesus as their Savior.
Jesus will come again to take all believers to himself. On the final day, all the dead will be raised. Those who are still alive will be bodily transformed. After this, the final judgment will take place. Unbelievers will go into eternal damnation, and believers into eternal life.
The true Christian Church is made up of all believers of all times who believe in the Triune God and in Jesus Christ as their only Savior.
The true visible church is the church which correctly preaches and teaches God's Word and administers Holy Baptism and Holy Communion according to the teachings of Scripture.
Christians are called to tell others that the only way of salvation is by faith in Jesus Christ, and to show their faith by their deeds of love towards others.