The psalmist sees himself as a weary traveler. The Lord leads him and prepares a table for him. The Lord anoints his head with oil, soothing him and cleaning him.
Every kindness is shown to the traveler.
The Lord's hospitality exceeds all others. A cup is something that you drink out of. The Israelites lived in a desert climate. Water was one of the most precious commodities of all. For someone to give you of their water was to give life to you.