What is the use of print(html) ? From where did the variable "html" came from ?

print() is a function which has one parameter, html. The print function will write something to the document. When you call the function you will pass an argument to it, which will be the actual value you want to print to the document.

for example

function print(html) {
  document.write(html);
}

const message = "<h1>!drloW olleH</h1>";

print(message);

In the video the print function is used to print out the list

function printList( list ) {
  var listHTML = '<ol>';
  for (var i = 0; i < list.length; i += 1) {
    listHTML += '<li>' + list[i] + '</li>';
  }
  listHTML += '</ol>';
  print(listHTML); //the listHTML is written to the document with the print function. The print function is declared below.

}

function print(html) {
  document.write(html);
}

In javaScript, functions can be declared anywhere in the javascript document (taken that the function and the calling of the function are in the same execution context and have been created using function declaration and not function expression) and they still work even if they are called before they are declared