Philippians 1:2 (ESV)

2 Grace to you and peace from God our Father and the Lord Jesus Christ.

The greeting is short, but also more than just a greeting: a blessing containing grace and peace. Grace is the undeserved(!) great gift that God gives in Christ. From that comes peace. Peace (also: from the OT) means much more than the absence of strife, disagreement, or war. Peace is the gift of a good relationship with God and with fellow human beings, harmony in all of life, well-being in all respects, flourishing of all of life. The words grace and peace are a summary of what is fundamental to the Christian faith. At the end of the letter these words return: the peace of God (Philippians 4:7), the God of peace (Philippians 4:9). And the grace of the Lord Jesus Christ (Philippians 4:23).