Definition of staking
"Staking means to buy stock in a poker player. The word "staking" should not be confused with "stacking" (taking all the chips from a player because you won a hand). Some people will want to buy stock in winning poker players. You can buy some or all of their action from a cash game or tournament. There are many forms of staking because it's all about the deal you have with the player you're staking.
An example of staking
A player is a big winner at NL200???. He has the bankroll to play NL200, but with his current expenses, he can't afford to move up to NL400???. A wealthier player might tell him "I'll stack you". When he stacks, he provides him with the money to play at the discussed limit. Generally, 50% of the player's profits will go to the staker and the other half will be kept by the player. The staker takes all the risk. If the player loses money in the NL400, it is the staker who has to pay. The same principle applies to tournaments.