Alright, little one, have you ever borrowed money from someone and promised to pay it back later? That's called a loan. Sometimes, when people borrow money, they tell the person lending them the money what they plan to use it for. For example, they might say they want to buy a new toy or go on a trip.
But what if something unexpected happens and they can't use the money for what they promised? That's where Quistclose trust comes in. It's a special type of trust that is created when someone lends money to another person for a specific purpose, but that purpose doesn't end up happening.
Let's say your friend lends you some money to buy a ticket to a concert, but then the concert gets cancelled. You can't use the money for what you promised, but your friend still expects you to pay it back. The Quistclose trust means that the money your friend lent you is still yours to use, but only in a way that will pay them back.
In other words, you still have control over the money, but only to make sure it can be used to pay back what you owe. This is different from a regular loan, where the lender doesn't usually care what you use the money for as long as you pay them back.
So, to sum it up, a Quistclose trust is a special type of trust that is created when someone lends money to be used for a specific purpose, but then that purpose doesn't happen. It allows the borrower to still use the money, but only in a way that will pay back the lender.