Confused with the second challenge

Here is some code that'll hopefully help you and others understand what Dave did for the second challenge. I was also super confused about this too but broke it down until it clicked.

Example: User inputs 10 for the starting number and 25 for the ending number.

1. The user inputs 10 for the starting number for the range.

var input1 = prompt('Starting Number?');

2. Then parseInt changes the input1 value from a string to a integer.

var firstNum = parseInt(input1);

3. User inputs 25 for the ending number for the range.

var input2 = prompt('Ending Number?');

4. Then parseInt changes the input2 value from a string to a integer.

var endingNum = parseInt(input2);

5. Takes the starting number and subtracts it by the ending number. Then it adds 1 so it won't be from 0 to -25 but from -1 to -25.

var calc1 = firstNum - endingNum + 1; 

6. Generates a random float number between 0 and up to but NOT including 1. Then it multiples that by the calc1 variable to make it a random float number that generates from -1.0 to -25.0.

var randomNum = Math.random() * calc1;

7. Takes the random float number from -1.0 to -25.0 and rounds it down to intergers that'll range from -1 to -25, no decimals.

var floorNum = Math.floor(randomNum);

8. Makes it a positive integer by adding the ending range number 25 to your random floor number. This Changes your negative integers to positive integers. It'll now range from 1 to 25. Feel free to try it in a calculator. Example: -6 + 25 = 19

var output = floorNum + endingNum;

9. The <p></p> are paragraph tags from HTML. It'll display on it's own line because it is a "Block-level element". The concatenation is performed to form a sentence to show the results from the output variable and to include the user's input value and output value.

var message = "<p>" + output + " is a number between " + firstNum + " and " + endingNum + "." + "</p>"; 

10. Finally, use the message variable inside the write() method to display the results.

document.write(message);

Thanks Steven Parker for the Markdown tip.