Determining Gapless Playback Info

I just downloaded the latest version of itunes and plugged in my ipod. immediatly, itunes stated doing this. It started scanning all of my songs and it took like 10 seconds for each song, and I was wondering, what is it and how often is it going to happen? Is it like defragmenting my ipod or something?

Should only have to do it once, then when ever there are changes. Just makes sure the space between certain continous songs does not cause the song to be broken into two songs.

http://docs.info.apple.com/article.html?artnum=304362