First of all, it's impossible to fully understand God because He is God and his ways and thoughts are higher than ours. Second the Bible clearly says that God is not willing that any should perish, but that all should come to repentance. However, people perish everyday (both physically and spiritually). So that must mean that God's will is different from what He actually allows to happen. He may will (or want) something to happen but it may not happen. That doesn't mean He isn't all-powerful, that just means He allows it to happen (just like he will allow the Antichrist to take over the world, proclaim himself God, persecute the saints of the tribulation and the Jews). If God did everything that He willed then there would have been no sin, Lucifer would still be a holy angel, there would be no death, sickness, etc. Obviously not everything God will comes to pass. I'm pretty sure God doesn't want (or will) these things to happen but He does allow them to happen. Again we don't know why, but we won't always know because God is God. God's second type of will is His plan. He has a plan that can be changed or delayed, not by human ability to destroy His plan but because He waits for us to do or not do something before He will allow His plan to be done (alot like how God wanted the Israelites to inherit the Promised Land after the Exodus but because they continued to rebel and disobey Him, He delayed their blessing and made them wander in the wilderness for forty years). God's final type of will is His definite unchangeable will (the kind that we humans can't change or delay). This is the same kind of will that will cause all of the prophecied end-times events leading up to the millenial kingdom to take place. I believe that when Jesus told his disciples to pray "Thy will be done" the phrase carried multiple meanings. It meant the disciples should pray that they would conform to God's plan, but also that He would allow His wants to take place. I say all of this to say that humans do indeed have free will and we can either conform our wills to that of our Heavenly Father or we can go our own way and perish. God does already know which choice we will make but he still allows us to make the choice.