If you wanted to print out something like this:
John says "What is your name?"
using double quotes you would get this error:
Parse error: syntax error, unexpected identifier "What", expecting "," or ";" in /home/althaus/public_html/infost440/a3/escape.php on line 14
To bypass this you could either use single quotes or use an escape slash.
You can see what it would look like using single quotes in the second line on the HTML Page.
This is what it would look like using an escape slash:
John says "What is your name?"
As you can see, visually it looks exactly the same but using the escape slash you still have the benefit of the double quotes where your variables and other characters get interpreted.
What the escape slash does is it escapes the normal functionality of the double quotes using the backlash. With that in mind you can use it to skip the dollar sign for variables so they don't show up as their value or to create a new line using "\n".
This is what a variable would look like with and without using an escape slash:
Henry has $amount US-Dollars (with escape slash)
Henry has 500 US-Dollars (without escape slash)