It's the first and most basic creed of the Christian faith: Jesus is Lord.
It's our answer to sin. Specifically, Jesus is my Lord. Jesus is the king of my life. I believe what he says — about me and everything else. I'm agreeing to live my life his way to the best of my ability.
It's the answer to the pain of this world, too.
When we are abused because of our faith, when we're faced with temptation or trial, when the storms of life seem like they're going to overwhelm us "in your hearts revere Christ as Lord" (1 Pet 3:15).
If saving faith comes from "Jesus is Lord of my life," living faith comes from "Jesus is Lord of everything." He doesn't just direct our lives. He orders the universe.
We may not always understand what is going on. We may wonder why God is allowing it. When we feel adrift, alone, and abandoned, we have to remind ourselves "Jesus is Lord."
If we can do that, we can remain calm in the midst of the storm. And people will notice. That's why the next sentence is "Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have."
When people see our hope, our faith, our ability to rely on the fact that Jesus rules the universe, they'll want to know why we can be so calm in the midst of the storm. At that point they're asking us to tell them about Jesus. It doesn't get any better than that.