Verifiable Delay Functions (VDFs) are a type of computer algorithm designed to take a certain amount of time. Verifiable Delay Functions (VDFs) are part of blockchain systems and are used to ensure that certain operations, such as verifying a transaction, take a certain amount of time to complete.
Imagine you are playing a game with a timer. The timer has a certain amount of time, and you can't move on to the next part of the game until the countdown is over. VDF works in a similar way, but instead of being used for games, it is used to keep blockchain systems "secure".
For example, let's say a group is using a blockchain to manage their money. They want to make sure that someone can't easily game the system by making a lot of fake transactions quickly. To prevent this, they use a VDF to ensure that it takes a certain amount of time to verify each transaction, making it much harder for someone to game the system.