Simplest guide I can give you without missing important details. The “Christian god” is the living and true God, who created everything, who controls everything and who knows everything, including the hearts of every man. Through the disobedience of the first man, Adam, sin came into the world, and with sin came death. God is holy, so holy in fact that he cannot tolerate sin and must punish it with death. Therefore because Adam broke the agreement that he had made with God, he fell from the perfect state that he was created in. The worst part is that all mankind was represented by Adam, and so all of humanity has fallen and by nature is an enemy of God and is deserving of death. This corrupt nature causes us to sin in action too. Why is this so important? Because unless you understand and believe that there is a God, who is the creator and upholder of all, and that humanity has sinned against this God and in doing so has earned the just wrath of this God, nothing that follows will be of any consequence to you. As a result of humanity’s sin we face death, this leaves us in a dire situation. This is the greatest problem that man faces and is the reason why Christianity exists. God is just, this means He must give to us what we have earned, and by sinning we have earned death. But God is also loving and merciful and does not wish for humanity to perish in their sin so He devised a plan whereby He would send His son, who is God, to die for our sins, paying the price due to us and earning us salvation. And so, as is recorded in the gospels, God sent his only son, and named Him Jesus, which translates as, God saves. Jesus was born of a virgin, so He did not have an earthly father and so the sinful nature of Adam was not present in Him. He lived a perfect life, never once sinning, and after about 33 years He was crucified, He died, and He was buried. More importantly however, after 3 days, He rose from the dead, signifying that His sacrifice was accepted by God, and that any who believe in Him as Lord and Savior, are made righteous before God, because our sins are paid for by His perfect sacrifice and we instead are given His perfect life. We are also brought into the family of God, we have our nature changed so that we are no longer sinful by nature, and we will be, both in this life and the next, changed so that our actions will no longer be sinful. Everything I say isn’t something I have come up with, it is straight from the Bible and what’s more, it’s not just my interpretation but it’s the interpretation of the early church and the faithful church throughout the last 2000 years. The reason why we take the Bible as it is now as the word of God is because the early church did, and they were verified by miracles. We believe what we believe concerning who Jesus is, because it’s what is revealed in the Bible, and we believe the Bible is true because it’s what the church at the time believed. God’s word is also true, it has no inconsistencies, it stands the test of time and it has the power to change lives. Regarding differences between denominations, remember that catholic simply means universal, so the Catholic Church refers to all the followers of Jesus worldwide. Originally the Roman Catholic Church was the only church, but over time the church was corrupted and so it was later reformed by various Protestant reformations in Europe in the 15th and 16th century. Protestants are just Christians who don’t follow the Church of Rome. Lutherans, Methodists, Reformers, Baptists, Anglicans, and Presbyterians are different Protestant groups usually based on what country they came from. These days, many of these denominations have been corrupted by the world around them, so much sometimes that they go directly against the teachings of the Bible, this is one of the reason there are so many church splits, another being disagreements on certain issues such as baptism. I advise you to read the Bible, and then to find a church in your area that follows the Bible and preaches the gospel. No church will be perfect but avoid going to one that openly supports homosexuality or has women leaders, as there are clear directives in the Bible against these things.