It is a common misconception that hits refer to visits to a website. This is most common with people who are trying to promote how successful their site is. I tend to find that the offline media are the biggest culprits in referring to hits as a measure of a sites success. However claiming your site is a huge success because it has had 100,000 hits is a bit like claiming your are rich when you have have 100,000 Yen.
This is because a hit relates to any request for a file from a server. This means depending on how many files or elements there are in your page, every time it is downloaded or viewed multiple hits will be recorded. If each person that visits the site views 5 pages and each page contains 20 files then each visitor could be producing 100 hits on average. Essentially this suggests that it is possible to create the 100,000 hits from just 1000 visits.
Most SEO companies will focus on visits or unique visitors as a measure of increased traffic. So next time you see this quoted in the media ask yourself why that figure is being banded about and what that figure actually means? Also if your SEO company is quoting hits as a measure of success you may want to take a closer look.