What Is Boredom?

So I'm on Passover break from my school here in Israel, and after two weeks of nothing, that perennial enemy sets in; Boredom. I don't know, maybe I could force myself to stay in bed for another couple of hours, but it is 2:00, and even though I'm sick, I don't think I can read another page of this James Michener novel (Hawaii) without going insane (good book, though.) Anyways, I'm bored, very bored. And sick.

I got out of bed, threw some clothes on, and wander out of my dorm room. I then stood there, for half an hour, trying to decide what to do. I realized, about then, that without going anywhere, or doing anything, or even deciding what to do, that I was no longer bored.

WHY?
What exactly is it that changed in that half hour that made mre no longer bored. I still had nothing to do, nowhere to go, and a book that I really couldn't read another hundred pages of right then sitting on my bed, but that mind numbing feeling I have when there nothing to do was gone.

Some things, clearly, are not meant to be understood.