Today's reading introduces us to the Book of Revelation, also known as the Revelation of John, because it is a revelation from Jesus to John. The purpose of the revelation is to strengthen John and the church. They faced persecution, and things would likely get worse before they got better. In that situation it was important for God to remind the church that God was in charge. That's the big picture message of Revelation: God's love wins in the end.
Revelation is hard to read because it is a vision. Like dreams, things happen in Revelation that don't make sense. The language is very symbolic and fantastical. Our passage today features Jesus with a sword coming from his mouth. I think the key to reading Revelation is to take it in stride. Don't try to figure out exactly what it "means" but look for the bigger message. While it is at times violent, over all Revelation is a message of hope for the church. We always need that hope, so listen to what the Spirit says to the church.