Question: "What does the Bible mean by binding and loosing?"
Answer: The concept of "binding and loosing" is taught in Matthew 16:19 and 18:18, "I will give you the keys of the kingdom of heaven; whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven." In this verse, Jesus is speaking directly to the Apostle Peter, and indirectly to the other apostles. Jesus' words meant that Peter would have the right to enter the kingdom himself, would have general authority therein symbolized by the possession of the keys, and preaching the gospel would be the means of opening the kingdom of heaven to all believers and shutting it against unbelievers. The book of Acts shows us this process at work. By his sermon on the day of Pentecost (Acts 2:14-40), Peter opened the door of the kingdom for the first time. The expressions "bind" and "loose" were common to Jewish legal phraseology meaning to declare forbidden or to declare allowed.
Peter and the other disciples were to continue on earth the work of Christ in preaching the gospel and declaring God's will to men, and were armed with the same authority as He Himself possessed. In Matthew 18, there is also a definite reference to the binding and loosing of church discipline. The apostles do not usurp Christ's lordship and authority over individual believers and their eternal destiny, but they do exercise the authority to discipline and, if necessary, excommunicate disobedient church members.
Christ in heaven ratifies what is done in His name and in obedience to His Word on earth. In both Matthew 16:19 and 18:18, the syntax of the Greek text makes the meaning clear. What you bind on earth will already have been bound in Heaven. What you loose on earth will already have been loosed in Heaven. In other words, Jesus in heaven, looses the authority of His Word as it goes forth on earth for the fulfillment of its purpose.