Indeed. It's basically Google and other search engines crawling forums. Most forum scripts have inbuilt accounts for Google etc.
Robots are a good thing as they will reference our threads in search results on the web. This is why we need to up the content. Build it and they will come lol. I hope to add some more tutorials next week if i get time
Not all of them - a lot are spam bots trying to get through registration to post spam. They can impact on server cpu & memorry usage as they will often have multiple hits going on at once & can become a virtual DOS. I would recommned the admins firewall the IP of those bots. There are plenty of sites that will give info on IP's of spambots. I use this one a lot & I believe there is an api for xenforo. https://www.projecthoneypot.org/list_of_ips.php