Mac mini keeps "indexing" my external hard drive.

[Roofy.]

I have no idea what this is and I'm finding it very annoying. How do I get this to stop? All of a sudden its doing this out of nowhere.

edit: OK....wow. Immediately after I posted this it stopped. But just in case this happens again, how do I prevent this from happening? And what is "indexing" more importantly?

 

[GGJstudios]

Spotlight: How to re-index folders or volumes
Excluding folders and disks from searches
Setting Spotlight preferences
Mac 101: Spotlight
http://en.wikipedia.org/wiki/Spotlight_(software)#Functionality

http://docs.info.apple.com/article.html?path=Mac/10.4/en/wn02.html

The intelligent search capability of Spotlight means you can find what you want, even across thousands of files. Spotlight also automatically notices when you add new files and it indexes the metadata within files, so it's always up-to-date and knows how to delivery highly accurate results.