I didn't understand it Can anyone explain it to me ??

I believe, it should look like this:

//Create function named max
//Which accepts two arguments x and y
function max (x, y) {
//Then comparing them using if/else conditional statment 
   if (x>y) {  
      return x;  //if x is larger than y, return x  
   } else { 
      return y;  // else return y
   }
}

max (5, 10); // should return 10

Thank you Grant Gasparyan I write it like this

function max (10, 5) { if (10 > 5) { return 10; } else { return 5; } }

but it's not true what is the wrong with it ??

For your code interpreter returns "SyntaxError: Unexpected number." I think it is because, you shuld not use numbers as an arguments while creating function, arguments are variables inside the funtion, so they should be called like variables. You can pass the values, while function call.

if we replace the number attributes to x and y arguments

function max (x, y) { if (x > y) { return x; } else { return y; } } 

and then call function passing values for arguments

 max (5, 10) 

it should work.

or You can call function right away, by wrapping function in brackets, like this

(function max (x, y) { if (x > y) { return x; } else { return y; } } ) (5, 10)

It's work :) Thank you so muck