[user104658]

Originally Posted by Niamh.

what does shortening and drifting mean (I'm not a gambler lol)

Shortening means (technically*) that the bookies think they are more likely to win and you will therefore get less money back for whatever you put on. Drifting means the opposite - less likely to win, more money back if they do.

* I say TECHNICALLY because bookies also manipulate odds for other reasons, for example, to attract bets to a selection that they do NOT think will win. They will cut the odds on a horse / team / BB housemate etc. to make people think "Ooooooh they must be more likely to win I will bet on them!!" when actually that is exactly what the bookie is trying to get you to do...

Odds are also affected by simply how much money has been bet on a selection. The more money has been placed across the country, the more the odds will come in to compensate. That said, for something like reality TV, looking at how much money has been bet on a contestant is actually quite a good indicator of how popular they are.