Stewardship is best described as "managing the affairs of another person". Historically the term would have been used of the household manager (an employee of the master of the house) who had responsibility to deal with domestic affairs. They would often manage the accounts and ensure other employees received wages etc. Characteristics of these stewards would include trustworthiness, loyalty to the master, fair dealings with others and the desire to act in the best interest of the Master at all times.
Stewardship is a concept which is often found in the Bible. In Genesis 1:26 God gives the people he has made the job of ruling over the created world. In Genesis 2:19-20 Adam is put in charge of naming the animals. This is often taken as a sign that Adam was to be God's steward for the created world.
In the New Testament in Luke 16 Jesus tells a story about a steward who is wise by the world's standards. His employer plans to sack him but on hearing about it the Steward quickly calls in some of his master's debtors. He still has responsibility for the accounts and he quickly lowers the men's debts wiping significant value from the remaining amounts to be paid. His thinking was that the men who had their debts reduced would look after him when he was out of a job.
Jesus then goes on to say that if we want to be good Stewards we must:
"use worldly wealth to gain friends for yourselves, so that when it is gone, you will be welcomed into eternal dwellings." Luke 16:9 (NIV)
What Jesus is saying is that we must use all the resources we have been given (our worldly wealth) in order to make friendships that will last beyond death into the next life. In other words we must use what God has given us in this life to prepare ourselves and others for heaven. We can't take anything with us so we must invest in heaven! See also Matthew 6:19-20.
That is why Jesus goes on to speak about the love of God and the love of money. A good steward will recognise that the money God has given to them is to be used in His service: to spread the gospel and to prepare other people for eternity. A man who loves money will simply want to get more of it in order to do what he wants with it, and so, as Jesus says, they end up serving it (working with all their energy for more of it) instead of using it to serve God.
True stewards have to master the use of the things of this world in the service of God instead of allowing themselves to be mastered by them. It is when we use resources wisely for God's kingdom that we are responsible trustworthy servants who can be trusted with the “true riches”, of God's kingdom (see Luke 16:11-12).
Sadly many Christians have more in common with the Pharisees in Luke 16:14 than with Jesus' teaching. They want to get what they can from God in this life, rather than looking for opportunities to serve Him with all that He's given with the hope of Heaven spurring them on.
Perhaps we all need to study the topic of stewardship and measure our attitude towards wealth using Jesus' teaching in Luke 16 and Matthew 6!