Who is this Jesus? How can you be sure you can trust what the Bible says? You have questions, we have answers!
Jesus is the one and only son of the one true, holy God. We could never do what's needed to live a holy, sinless life and be in the presence of a holy God. Like someone paying a debt they don't owe, Jesus paid the penalty for us when he died on the cross after living a sinless life. But he didn't stay dead! He conquered sin and death when he rose again on the 3rd day.
The Bible is a compilation of 66 books written by at least 40 different men over a period of roughly 2000 years. Even with this, the Bible remarkably never contradicts itself, tells a consistent whole story thoughout, and predicted many future events with prefect accuracy. It has never been--and never will be--contradited by science. And it gives us divine answers about the nature of the universe. For a more indepth answer, check out this article by Answers In Genesis.
Sin is anything we think, say, or do that goes against God's law. Because the first man Adam sinned we are all born sinners. Romans tells us that ALL have sinned an fallen short of the glory of God (Romans 3:23).
When you look through the basic law of the 10 commandments it might be tempting to think, "I'm not that bad, I'm doing alright!". Yet when we read through the Bible as a whole, we see Jesus say that looking at woman with lust is equal to committing adultry (Matthew 5:27-28), and whoever calls another a fool will be judged to hell unless they repent.