Want to buy my house? It's worth $10,000,000 but you can have it for $100,000.
Oh wait it's a mobile home and it's not even worth $100,000.
That would be one example. But it can mean a lot things. Use it in a sentence if you like and I'll re-answer.
I used it in an earlier answer today when I was referring to someone that signed an exclusivity contract with selling Realtor based on that Realtor telling the seller he/she had a buyer. If that Realtor was lying, that would be a bait and switch. Make sense?
The same as it means in anything else. Advertise one, to get you interested and then say sorry but that one is gone, but I have another one for sale.