What does it mean to confess Jesus as Lord ? Let’s read the context:
Romans 10:1-13 “Brothers and sisters, my heart’s desire and prayer to God for the Israelites is that they may be saved. 2 For I can testify about them that they are zealous for God, but their zeal is not based on knowledge. 3 Since they did not know the righteousness of God and sought to establish their own, they did not submit to God’s righteousness. 4 Christ is the culmination of the law so that there may be righteousness for everyone who believes. 5 Moses writes this about the righteousness that is by the law: “The person who does these things will live by them.” 6 But the righteousness that is by faith says: “Do not say in your heart, ‘Who will ascend into heaven?’” (that is, to bring Christ down) 7 “or ‘Who will descend into the deep?’” (that is, to bring Christ up from the dead). 8 But what does it say? “The word is near you; it is in your mouth and in your heart,” that is, the message concerning faith that we proclaim: 9 If you declare with your mouth, “Jesus is Lord,” and believe in your heart that God raised him from the dead, you will be saved. 10 For it is with your heart that you believe and are justified, and it is with your mouth that you profess your faith and are saved. 11 As Scripture says, “Anyone who believes in him will never be put to shame.” 12 For there is no difference between Jew and Gentile—the same Lord is Lord of all and richly blesses all who call on him, 13 for, “Everyone who calls on the name of the Lord will be saved.”
Righteousness means to be sinless (as God Himself).
Israel trusted in their own works, trying to be righteous under the law. The Righteousness of the law said to obey the 10 commandments to be sinless. But nobody is righteous by the law because nobody can be sinless by their thoughts/words/deeds.
This is why Jesus Christ, the Son of God came to fulfill the law by His death on the cross and then He rose from the dead.
He died to end the law so that we are made righteous by faith in Jesus.
To confess Jesus as Lord means that you trust in Jesus and not in your works.
You confess that you are righteous by faith in Jesus and not by your works.
You agree that you have no works to be saved.
You trust fully in Jesus Christ – His death on the cross forgave your sins and His resurrection made you righteous. He did everything to save you and therefore you confess Jesus as LORD.