It is simply telling us how God cares for His covenant people, and is not restricted to only Israel (Jesus the Good Shepherd) but also is applicable to all those joined to Christ through faith. We are in the hands of the Good Shepherd, who provides, protects, guides, watches over, us, His flock. We need not fear even though we walk through the valley of the shadow of death for He is with us---as the Psalm begins the transitions to us, having set the metaphor of the relationship---sheep to Shepherd, Shepherd to sheep. The rod and the staff in the use of the shepherd are to defend against wild beasts, to direct and keep track of the sheep, the staff to rescue them from danger. Careful note should be made in the heart and mind of the reader, of the relationship (and a relationship it is.) He is in charge. He is the one with the wisdom and power and love and concern for the flock. We, the flock, can be at peace trusting in Him. "Do not worry or fret---" He says. Follow Him.