Living and True God simply declares two truths about God: He is alive and He is true. God is more alive than any of us can imagine and He sets the standard of truth.
Living and True God in Greek:
Ho Theos zōntos kai alēthinos
Strong’s Concordance numbers: 2316, 2198, 228
Bible reference: 1 Thess. 1:9
[Believers throughout Greece] report what kind of reception you gave us. They tell how you turned to God from idols to serve the living and true God. (1 Thess. 1:9 NIV)
Similar names for God are the Living God, Living Father, and the True God. Jesus is called the Living One, Faithful and true, and the Faithful and true witness.