Poor little orphans, someone should find them a wallet to call home.
So what's an orphan anyways?
It's a misnomer.
It's a block with no children in the main chain.
and it's parent has disowned it, not died
Basically, when 2 pools/people find a block at the same time, they are distributed around the internet.
Each bitcoind that receives them in the order they get them, decides either:
1) I've not seen any block at this height before. OK, I decide this is the next OK block
2) I've already seen a block at this height before, so you aren't the winner (but I'll hang on to you just in case that changes later)
The next network block will do the same thing and usually decide the winner as long as an orphan race doesn't happen with that block and thus repeat the process.
BUMMER
I remember the 1st ORPHAN! nothing was worse than the second block we ever found was a orphan.
I got over it (kind of) and just kept on hashing.
by my figurers it cost about 7BTC.
It's still the best pool you can point all your miners at.