solidity storage vs memory

storage vs memory

// SPDX-License-Identifier: ISC
pragma solidity ^0.7.0;

contract Storage {
    struct Test {
        uint256 id;
        uint256 count;
    }
    
    uint256 public storageId;
    mapping(uint256 => Test) public tests;
    
    function createStorage() external {
      storageId++;
      tests[storageId] = Test(storageId, 0);
    }
    
    function testStorage(uint256 _storageId) external {
        // should be storage to change the tests status
        Test storage t = tests[_storageId];
        t.count = 100;
    }
    
    /*function testStorage(uint256 _storageId) view external {
        Test memory t = tests[_storageId];
        t.count = 100;
    }*/
}