What is string_view

            This is lightweight, non-owning view(pointer) to a const sequence of characters. 
            [Example] Consider a window in your house, looking at a car parked on the street. We can look through the window and see the car, but 
            can’t touch or move the car. Your window just provides a view to the car, which is a completely separate object.
            It allows you to refer to a part or the entirety of a string without copying the data, which can lead to performance improvements in specific cases
        

#include <iostream>
#include <string_view>

int main() {
    std::string str = "Hello, World!";
    std::string_view view(str); // view references the string, no copy is made

    std::cout << view;  // Outputs: Hello, World!

    std::cout << view.substr(0, 5);  // Hello
}

Characteristics

Read-only: You can only read data through a std::string_view, not modify it.
No copying: Avoids the overhead of copying strings in many cases
create substrings without incurring the cost of allocation or copying data, unlike std::string, which creates a new object

Comparison

string_view vs const string&

fun(string_view s) fun(const string& s)
Substrings Can create a view on a substring without copying or allocating new memory. Requires creating a new std::string for substrings (incurs allocation and copying).
Null-Termination Does not require null-terminated strings (can point to non-null-terminated buffers). Assumes a valid std::string, which is always null-terminated.