Its one way some sites try to get you to visit their site. they artifically inflate your stats by calling a file on your site a few times and on low traffic sites usually 20-30 hits would make this referrer appear high or at the top on your referrer list, making them more visible. The spammers know that 99% of the sites out there have little or no traffic, and hit the site a few times to make sure they are high on the referrer list.

They assume you will click through to their site to see who is referring you.

Just another type of spam. You can block that site in .htaccess if it bugs you.