How this feature works?

Given the following code, which gave rise to questions

#include <iostream>
#include <fstream>
using namespace std;

void insert(list*& p, char value); 

struct list
{
 char symbol;
 list* next;
};

int main()
{
 setlocale(LC_CTYPE, "Russian");
 list* first = nullptr;

 char value;
 cout << "Enter a character ";
 cin >> value;
 insert(first, value);
}

void insert(list*& p, char value) // 
{
 list* newP = new list;
 if (newP != NULL) //is there a place? 
{
 newP->symbol = value;
 newP->next = p;
 p = newP;
}
else
 cout << "insert Operation failed" << endl;
}

1. The insert function takes two parameters, for which the first parameter? Why refer to the insert function pointer to reference the first parameter?
2. list* first = nullptr - it Seems in this line creates a pointer to the first element of a single-linked list, why would it assign a void?
3. What is happening in this line? list* newP = new list;