If I can persuade you to sell to me for $2,300 an antique desk that’s worth $5,000, that’s a transaction at an undervalue
If you’re going into liquidation next week and you and I have been friends for many years, you owe me $1,700, so the week before your declare yourself bankrupt you pay me the $1,700 in full, that’s a preference – you’re preferring me above the rest of your creditors