I was intrigued too but it's explained in the FF.net explanation pages. Well, I had found it there.
A hit is one time a page is checked.
A visitor is a person that checked that page.
The difference ? 1 visitor can click on a page 50 times in a day => 50 hits. Even if it is on the same chapter (= page). But it shall be accounted as only 1 visitor anyway in terms of IP address. If there are 2 people behind the same computer reading a story, it still shall be accounted as 1 visitor.
Therefore, visitors are much more important a stat than hits. Hope this will help.
I am pretty sure that means that 284 people have looked and clicked on you story but 119 people have read it. i am also new to fanfic my username summerlover4223, and I was confused about that too. If I am wrong oh well. Either way you still have readers :) and you can add me on fanfic