When deploying to Testnets, you will hear the concept of faucets. A faucet is a web application that will send your wallet address a certain amount of test SOL. Test SOL allows you to understand that the contract you have prepared is working correctly by paying the gas fee you need to pay to perform transactions with test SOLs and distribute your contract, without using the real SOLs in your wallet. After you make sure that the system is working correctly, you deploy it on the Mainnet and pay the transaction and gas fees. 

Each testnet has a different set of faucet options. Stakely's Solana Faucet, SOL Faucet are most commonly used Testnets on Solana.

Resources:

https://moralis.io/ethereum-testnet-guide-connect-to-ethereum-testnets/