Typically search engines use spiders to gather information from web sites to increase there search index.
example search engine spiders:
- ask jeeves
AdminCP > vBulletin Options > Who's Online Options
- Enable Spider Display - Setting this to Yes will allow you to see the spiders you have specified in the Spider Identification Description
- Spider Identification Strings - Enter the unique identifier for the spider you want to see
- Spider Identification Description - the description of the spider to be displayed in the Who's Online section of your board