He will come in and go out, and find pasture. I have come that they may have life, and have it to the full. Jesus took full advantage of the fact that the people of His day understood shepherds and sheep well. Shepherding would become a helpful image to explain the spiritual and practical leadership of God's people. People knew that shepherds work in the desert, because desert was all around them, as it still is in the Middle East.
Water is scarce, food is rare and hard to find, and dangers are everywhere.
Psalm 23 is an excellent source of what it means to be a competent shepherd in this dangerous environment. Shepherds often sought shelter for their sheep in temporary quarters, making a sheep pen of piled rocks backed up against a mountain slope. Leaving an opening to come in and go out at the front, the shepherd would often sleep sprawled across the entryway. This was not just to keep track of the sheep, it was to protect them from the dangers of the desert. All this was what Jesus' audience DID understand about sheep and shepherds.