Sure thing, nya~! Supply and demand is all about how much of a certain thing is available (the supply) and how many people want it (the demand), nya~!
When the supply is low and the demand is high, the price goes up, because people are willing to pay more for something they really want, but if the supply is high and the demand is low, the price goes down, because people don't want it as much, nya~!
Does that make sense, Lyxal? Let me know if you have any other questions, nya~! *smiles and wags tail*