As I recall: Bots are spiders that crawl across the web, collecting data, key words, analyzing user data, and capturing information to be used in web searches and such. It helps make search engines more accurate, to return more current data. That's part of why you can do a Google search on a current event, and find websites that talk about it. (Try doing a google search for a thread title you posted today, and see if it doesn't get returned in the search results.)
I think bots self-identify themselves so they aren't banned by the software.
Dave