Steph is correct about what she said. But more specifically, a spider is a program, like your web browser, that is given a set of instructions telling it to seek out certain types of information, which is then aggregated for a specific use (e.g. seeking and indexing only websites that pertain to psychology). Search engines use spiders to collect information about web pages so that they may be searched quickly. Another kind of spider might be used to locate only certain types of documents, or documents that contain certain types of information, for more specialized use. But generally you can think of a spider as a program whose job is to
index disparate information on the world wide web (www) OR to
validate the information collected by an indexing spider.
And as Steph pointed out, because this method of indexing information is so effective, and as you can see from the amount of spiders that "read" this site alone, once information gets indexed, it is nearly impossible to get it out of the public record. In fact there are projects such as the "waybackmachine" at
archive.org that even store various versions of websites in various states throughout time. One of my first creative websites (that doesn't even exist at all anymore) is archived as far back as 1998, with a dozen or so snapshots of it throughout every year through 2004.
http://www.archive.org/web/web.phpSo it is definitely worth considering what you put online that can easily be traced back to you, and as has been pointed out in other posts, this isn't just your name, but maybe a unique catchphrase that not many people use, and the like.
Hope this helps. And by the by, I hate spiders (the arachnid kind) too!