RPICoin is a full PoS (Proof of Stake) coin and can't be mined in the usual way, you only need to leave the RPI wallet running instead of requiring expensive and energy consuming hardware.
So this switch from PoW to PoS provide the following benefits:

• Energy savings;
• A safer network as 51% attacks become more expensive;
• Affordable for Users– In addition to less energy consumption, the Proof of Stake system allows more users to take part in the forging process. Where for (PoW) expensive mining- rigs / hardware is needed.

The staking reward is fixed at 300RPI each stake.
Depending on how much coins you have in your wallet (your weight vs network weight) you will receive stakes more- or less frequently.
When running the wallet 24/7 (unlocked state) the Staking rewards will earn you 45% of your total amount of coins held in your wallet over the period of a year.

Staking is a kind of a lottery as some days you will receive more stakes than usual, some days less. The more coins you have, the more you will get.
There's no predicting exactly how many stakes you will get. However, if you stake with more coins, you get more blocks and you more likely to find a reward. Someone staking 24 hours a day, 365 days a year would get more than someone staking the same amount of coins an hour a day.