When the word ‘LORD’ appears with all letters capitalized, this refers to GOD. ‘Lord’ is a reference to our Lord Jesus Christ–our Redeemer!
LORD = the one and only true GOD; the Creator; our heavenly Father. “Unto thee it was shewed, that thou mightest know that the LORD he is God; there is none else beside him.”–Deuteronomy 4:35
Lord = Jesus Christ, the Son of GOD; ‘our Savior’ ⇒ our Messiah and the only way to the Father. “Jesus Christ is truly God, the Second Person of the Trinity, the Son, the Eternal Word, who with the Father and the Holy Spirit always was, is, and always will be.” † I and my Father are one.–John 10:30
lord = a human ruler
For there are three that bear record in heaven, the Father, the Word, and the Holy Ghost: and these three are one.—1 John 5:7
A Matthew Henry Commentary (regarding 1 John 5:7): “The Father, repeatedly, by a voice from heaven declared that Jesus was His beloved Son. ¹ ² ³ The Word declared that He and the Father were One, and that whoever had seen Him had seen the Father. And the Holy Ghost, who descended from heaven and rested on Christ at His baptism; who had borne witness to Him by all the prophets; and gave testimony to His resurrection and mediatorial office, by the gift of miraculous powers to the apostles; But whether this passage be cited or not, the doctrine of the Trinity in Unity stands equally firm and certain.”