Question: "What does the Bible mean by binding and loosing?"
Answer: The concept of “binding and loosing” is taught in the Bible in Matthew 16:19: “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, that he would have general authority symbolized by the possession of the keys, and that 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 something forbidden or to declare it allowed.
Peter and the other disciples were to continue Christ’s work on earth in preaching the gospel and declaring God's will to men, and they were armed with the same authority as He possessed. In Matthew 18:18, there is also a definite reference to the binding and loosing in the context 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 have already been bound in heaven. What you loose on earth will have already 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.