How assignment to variable located in storage works?

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Ethereum

I'm reading solidity's readthedocs, and in the section Data Location there's this contract

pragma solidity >=0.4.0 <0.6.0;

contract C {
    uint[] x; // the data location of x is storage

    // the data location of memoryArray is memory
    function f(uint[] memory memoryArray) public {
        x = memoryArray; // works, copies the whole array to storage
        uint[] storage y = x; // works, assigns a pointer, data location of y is storage
        y[7]; // fine, returns the 8th element
        y.length = 2; // fine, modifies x through y
        delete x; // fine, clears the array, also modifies y
        // The following does not work; it would need to create a new temporary /
        // unnamed array in storage, but storage is "statically" allocated:
        // y = memoryArray;
        // This does not work either, since it would "reset" the pointer, but there
        // is no sensible location it could point to.
        // delete y;
        g(x); // calls g, handing over a reference to x
        h(x); // calls h and creates an independent, temporary copy in memory
    }

    function g(uint[] storage) internal pure {}
    function h(uint[] memory) public pure {}
}

At the line

uint[] storage y = x;

I would have thought that y is the exact same type as x and therefore behave exactly like x, but it's not the case as shown in line

y = memoryArray;

The comments in the code are confusing to me. Is there a clear explanation of how this works?

What I have tried:

I tried to understand their comments without success...