Users will be able to delegate their stake, or to act as stake pools and have stake delegated to them.
According to the latest information Cardano (ADA) should have 25-100 pools when Staking era starts (Q2 2018).
Why are staking pools important?
Users of Cardano will be able to vote on upcoming updates and protocol changes, using their stake.
In a fully decentralised network, software and protocol updates should not be decided by a central authority. To ensure that its protocol can be developed over time, Cardano will have a voting center for updates. Updates to the software and the protocol can be proposed, and users will be able to vote on those proposals, weighted by the amount of stake they hold. Users who do not want to concern themselves with technical details may delegate their voting rights instead, and trust a stake pool to make an informed and responsible decision on their behalf. (https://cardanoroadmap.com/)
What is the reward for Staking Ada?
You can use this calculator – ada-calc.herokuapp.com (This site is unofficial and the result is approximate. We can’t guarantee your future rewards.) Rewards from non-issued ADA only, from transaction fees are not included.
Cardano (ADA) will be minted. 1 block duration is 20 seconds.
2,000 ADA per block for the initial 3,744,961 blocks,
1,000 ADA per block for the subsequent 3,744,961 blocks,
500 ADA per block for the subsequent 3,744,961 blocks,
and so on and so forth, in such a way that the ADA per block will be halved every 3,744,961 blocks.
Given that 3 new blocks will be generated every minute, 99.95% of the additional 14,979,843,678 ADA necessary to reach the 45,000,000,000 ADA will be issued in approximately 24 years.
Of the ADA that will be issued per block: 75% of it will be given to the protocol participants as a block reward. 25% of it will be directed to a special address that is earmarked for the Cardano Treasury, from which developers and ecosystem participants could request the funding of their projects, and the stakeholders of the system would vote to approve or reject their proposals.
Minimum amount needed to stake Cardano to a pool: 1 ada.
More detail coming soon.