Christians believe that Jesus came to earth to die for our sins. John 3:16 says, "For God so loved the world that he gave his one and only son, that whoever believes in him shall not perish but have eternal life." Eternal meaning forever in heaven. God first created the world so that people would get to know him so they could spend forever(eternity) with him in heaven. However, Adam and Eve sinned because they were tempted by the evil one. (which is why Jesus came to Earth to save our sins!) Romans 3:23, "For all have sinned by fall short of the glory of God." We all sin and we can NEVER compare to God. God is SO great and SO mighty. We long to be like him. By reading the bible and praying we can come to know God more. If we live what the word (the bible) says we can be more like Christ. However, that is not how you "become a Christian". If you would like to live with the Lord forever in heaven and if your committed to living for God then you must ask (pray to) God to come into your heart. Now, of course I can't tell you EVERYTHING in one little post. There's MUCH more to write about! So if your interested in what Christianity is all about I suggest you find a church and attend services. Even going to a youth group is great! Find a pastor/youth pastor or just a trusted adult (who goes to church!) and ask them more about what this who "Christianity" thing is really about. You won't regret it!