Firefox add-on questions

Avast Free Antivirus / Premium Security
1

Hi. I just purchased Avast! a few days ago, and have some new-user questions, particularly regarding the Firefox add-on (Avast Online Security 9.0…).

  1. Quite simply, does the virus-protection itself work without this add-on? Or is it just an extra that warns you about sites. etc.?

  2. On that subject, what does “this site has a bad reputation” mean? Does that imply that the site is actually dangerous (as in harmful to your computer), or just a disreputable company, that kind of thing?

  3. About the little button on the right side of the toolbar (with the green Avast! logo on it), I don’t understand what the number on it represents. What does it mean when it says that 3 companies (or whatever) tried to track me? And tried to track me since when? Since I last opened the browser?

Any help would be appreciated. Thanks!