First thing's first, Cardano is a blockchain network, much like Ethereum or other networks that you might have heard of.
Within the Cardano network comes Cardano wallet, a tool that helps you interact with the blockchain, whether it is to send, receive, store or stake its own currency, ADA. Every ADA holder also holds a stake in the Cardano network. ADA stored in a wallet can be delegated to a stake pool to earn rewards
When setting up Cardano Wallet, private key and public key are generated. Your wallet is generated by the public key, meaning you can share it to receive ADA. On the other hand, your private key will be used to digitally sign your transactions to send ADA to other wallets within the network.
There are two ways ADA holders can gain rewards: by delegating their stakes to a stake pool or run their own stake. The more stake is delegated to a stake pool, the more likely it is to make the next block – and the rewards are shared between everyone who delegated their stake to that stake pool.
From here you must have gotten the sense of what Cardono is, how it works and what you would gain from joining a pool. Next is to create your own Cardano wallet, get some ADA and start staking.