A Christian Steward is. someone who takes care of what belongs to someone else, like an administrator, an executer, or trustee -- NOT an owner.  Christian Stewardship recognizes that everything really belongs to God -- everything we are and everything we have -- and that God will hold us accountable for how we use the many gifts He has entrusted to our care.  

If we truly believe this and experience a conversion of the heart, we can't help but respond with profound gratitude.  This gratitude is expressed in our celebration of the Eucharist (the very word means thanks) and in the way we live our everyday lives.  All our time, our talents and material possessions are gifts and blessings from God to be used in such a manner that tells the world that "Christ is my Savior and I am His disciple." 

In their Pastoral Letter "Stewardship: A Disciple's Response" the American Bishops describe a Christian steward as: 
 
"One who recieves God's gifts gratefully, cherishes and tends them in a responsible and accountable manner, shares them in justice and love with others, and returns them with increase to the Lord." 

The Parable of the Bags of Gold is a wonderful bible reading summarizing stewardship to our Lord.  
Matthew 25:14-30 The Parable of the Bags of Gold.