If you read the example you will notice that it adds +1 to the counter each time somebody enters there.
is this for online counting? for example: "Now 3 online visitors". Or for general counting?
So, if you put it somewhere on your main page, it will tell you how many people read this page.
If you clear the content of the file each morning, at the end of the day it will tell you how many people today. If you don't clear "alle.txt" it will tell you the total number since creation of the file.