A.k.a. web crawler, spider, or spider bot. It's a bot that searches and scrapes your website data. It can gather URLs (the links on top of the browser), meta tags, and any kind of content (images, video, text) for many types of uses. Search engines (like Google) index everything on the whole web with their crawlers, so users don't get mad with loading screens and can view short summaries of what the website is all about.