This is generally the process of holding coins or tokens in a wallet to support a particular blockchain or application. People typically do this to support network operations in return, typically, for some type of reward.
Depending upon the system, there might be time commitment as well as a certain period to unstake.
Staking is viewed as a greater level of commitment than simply holding the cryptocurrency in liquid form.
With gaming, players often stake in-game digital assets to increase their powers or gain some benefit they did not previously have.