What is the difference between offsite and onsite web analytic tools?

Question

What is the difference between onsite and offsite analytic tools?

I am reading a book about web analytic tools and this is the definition (from the book):

Offsite web analytic's tools measure your potential website audience. They are the macro tools that allow you to see the bigger picture of how your website compares to others.

Onsite web analytic's tools measure the actual visitor traffic arriving on your website.

This doesn't make the distinction clear to me. I generally understand about onsite tools, but offsite tools doesn't make sense.

Solution

Offsite analytics would include any tools that analyze traffic on your website through tools not served with the web page or directly connected to the web server in any way.

A good example would be Google analytics which can give you a good idea of the amount of traffic on your site, but because it does not have direct access to your website can only show traffic coming from Google. Another example would be Alexa which gathers data derived from various browser plugins to see how much traffic a site receives.

Onsite analytics would include tools like Google Analytics which is served as a cookie with the webpage, and cPanel's built in analytics would also be included since it directly monitors the traffic to and from your web server.