Variable Scopes and Visibility Modifiers

State variables: Variables whose values are permanently stored in a contract’s storage. We can refer to them anywhere in the contract in which they are declared, and depending on their visibility in other contracts.

Local variables: Variables whose values are only stored during the execution of a function and can only be referred to within that function.

Globally available variables: Predefined variables that provide information about the blockchain. They can be referred to in any Solidity contract without having to declare them. ...