View and Pure Functions in Solidity

view indicates that the function will not alter the storage state in any way. But it allows you to read the state.

pure is even more strict, indicating that it will not even read the storage state.

A pure function is a function which given the same input, always returns the same output. But the state of the contract keeps changing as users interact with it. So if you pass a state variable as an argument to the function, since the state is changing, that function will not be pure. That's why pure functions cannot access to state.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.15;

contract ViewAndPure {
    uint public gamePoints = 0;


    // No modification or reading from the state
    function checkRewards(uint multiplier, uint points) public pure returns (uint) {
        return multiplier * points;
    }

    // No modification but can read from the state
    function addGamePoints(uint newScore) public view returns (uint) {
        return gamePoints + newScore;
    }

}

If you call view or pure functions externally, you do not pay a gas fee.

Read more about storage and memory here