Its way to run a script that send a robots to access your website URL and this action convert in to visit and display in server log when webmaster review site traffic but it’s all entirely fake because its software generated visit not natural.
Why People doing this?
Many site leave open their server log stats for search engine crawlers - so you can gain crawlable links from valuable university and government sites easily.
You can gain significant traffic from webmasters checking their logs, finding you in the referrer lists and clicking through to see what you’re saying about them.
These two are main purpose people doing referrer spamming but it’s not more effective because search engine crawler sometimes catch this fraud work and penalize your site.