What is Referrer spam?

Referrer spam is a bit spamdexing. The method occupied making repeated web site requests utilizing a fake referrer URL that points to the site the spammer needs to advertise. Sites that broadcast their access logs, with referrer statistics, will then end up linking to the spammer's site, which will in turn be indexed by the search engines as they crawl the access logs.

What is your opinion?

its a form of black hat seo, dont do it

Thank you for replying me buddy. I hope this information helps you somewhere. Keep replying.

Referrer spam is a kind of spamdexing. It’s not a usual SEO technique. It’s a black hat practice that is being used less and less now that Google is becoming more and more familiar with it in addition to creating spam links less important.