Web3 digital wallets are essential to access the DeFi and crypto. Basically, they have the ability to store digital assets. This includes everything from fungible to non-fungible tokens (NFTs). Digital wallets also allow you to interact with dApps on various blockchains and you can access an extensive dApp ecosystem.

There is a wide range of wallets on the market that have their own strengths. Some of the most popular ones are MetaMask, Coinbase Wallet, Trust Wallet, and Argent.

After creating the smart contract and testing its security, it is necessary to deploy it to the blockchain so that users can interact with it. When talking about deploying a smart contract, there are two options:

Testnet:  Testnets are test networks that you can deploy your smart contracts for testing. These offer a low-cost/risk environment for working with a smart contract. The tokens and transactions on a testnet are not connected to those on mainnet. 

The main benefit of using a testnet is that they operate in a similar way to the mainnet so you can have a better understanding of how your contract will function before deploying it there. Since you make test transactions with test coins, there is no expense from your assets in your wallet.

Mainnet: Mainnet is the live network of the Ethereum blockchain. You want to make sure that your contact has been tested and audited before deploying it here. Your contract will now be fully accessible to any address and they can start to transact with it. There are gas fees that you will need to pay to deploy and transact with your smart contract. 

Resources:

https://moralis.io/what-is-a-web3-wallet-web3-wallets-explained/