The Church of Jesus Christ of Latter-day Saints was founded by Joseph Smith in 1830. We believe that Jesus Christ is the only perfect person to ever live on earth, and that He called Joseph to be a modern-day prophet to help bring back the original, pure church of Christ that we can read about in the Holy Bible. Many Christian churches came about by a reformation (changing of what already existed), but the Church of Jesus Christ of Latter-day Saints came about through a restoration, or a bringing back of the original church of Christ.
I would like to emphasize why the return of Christ's church to the earth is so important. It's safe to say that at some time, many people wonder about major life questions. For example, people may wonder what the point of life is. Are we here by accident? I can tell you that the answer is no. Some people may also wonder if there are specific things we can do in our lives to make the best out of it. That answer is yes! With Christ's church back on the earth, we can be taught about Christ and his plan of happiness. It has the same direct revelation, or spiritual communication with God nowadays that it did when it was first created. That means that God speaks to all (just like in times past), and that can help people live the best lives possible. There are so many temporal and spiritual blessings awaiting for those who follow Jesus Christ.