Beagle is an indexing and search tool, that I was glad to be rid of. For me it interrupted me by starting to index even when set to index only when the computer is idle, and was a huge resource hog. My cpu would run close to max for 15 minutes and on my laptop the temp would go up where I don't like to see it. As far as the search capabilities it didn't do a much better job than the default gnome search tool.
Beagle seems to have been replaced in Fedora by Tracker, another indexing and search too. It's not (quite) as big a resource hog as Beagle, and will run when idle if set to. Again though, I don't see the big advantage over the default search tool. If it's faster the difference isn't enough for my eyes to detect.
I am root the great and powerful
Pay no attention to the man behind the curtain