Billy, Satan does exist, and, for now, he is in charge of the world.
God created the heavens and earth for his creatures, and heaven was created for his first creatures - the angels. They are beautiful creations, Billy, endowed with intellect and free will. The pinnacle of of these created beings was Lucifer - the angel of light.
Lucifer discerned that he was better than all of God's creations and pride grew in him. However his pride was not for the Creator, but in the creation - himself. He determined that he, Lucifer, should have the same power as the Creator and he led a rebellion. A war ensued and Lucifer lost. He and his followers were banished from heaven, but this banishment was never meant to be permanent. You see Billy, God still loved his creation. So, he banished them with the hope they would repent. Though Lucifer was banished from heaven, he is still allowed to approach the throne of God as we see in book of Job because God still carries the hope that Lucifer will repent. In the meantime, Lucifer has no kingdom or home of his own.
So Billy, God tried again. He creates a new place and a new creature. Instead of a spiritual place with spiritual creatures, God creates a physical place and physical creatures. You see Billy, God has an order to his creations - the first is last and the last is first. So these new creations were even more spectacular than the first; ending with man and finally the most beautiful creation - woman. Just like the angels, man and woman were created with intellect and free will.
Lucifer saw the man and woman - Adam and Eve - and became jealous. In his mind these new creatures were inferior to him and yet God gave them a kingdom - earth. Lucifer decided he would wrest this kingdom from Adam and Eve for himself, and he would work on the best of God's creations - woman.
Keep in mind, Billy, Lucifer is a spiritual creation and Adam and Eve are physical beings, so Lucifer had a problem. How can he wrest the deed to earth from Eve if she can neither see nor hear him? Lucifer decides he must use a physical vehicle to approach Eve, and that vehicle was the snake.
Lucifer wants the deed to the earth, but he also wants to humiliate God and God's new creation. When God placed Adam and Eve in the Garden, there is was only one area of prohibition (or as we call it, sin). They were told not eat the fruit of the Tree of Knowledge of Good and Evil or they would surely die. Lucifer, disguised as a snake, used this one prohibition to tempt Eve. Eve knew the prohibition for we see that she stated that she would die if she ate the fruit of this particular tree. Yet, when Lucifer told Eve that if she ate the forbidden fruit, she would be like God, she decided to go for it. I find it amusing, Billy, that Lucifer did not use a little more imagination for he used the same sin on Eve, pride, that cause his own downfall.
So Billy, what did Lucifer get from Eve in return for the information that the fruit of the forbidden tree would make her a god? He got the deed to the earth. Now he had a kingdom; a home.
To finish the story, Adam ate the fruit and both he and Eve experienced spiritual death. Though God mouned the loss of his finest creation, he must keep his Word. So, God issued a caveat. The sin can be expunged by a living sacrifice.
Billy the plan of salvation is this. One sin - you die a spiritual death or separation from God. To expunge this spiritual death, you must perform a living sacrifice. As every man and woman has sinned at least once in their lifetime, we are all walking around dead, so anything we do will not meet the requirements of salvation. Only one man - Jesus - lived without sin. He was the living sacrifice and by choosing his sacrifice, we have been expunged.
So you see Billy, God made everyone equal - salvation is not who you are or what you do; Salvation is a Choice. Salvation just like Sin is a product of our Free Will, and if I may parapharse Francis Church one more time. Jesus Lives!
* Paraphrased from Francis Church, The Sun Newspaper, 9/21/1897