Okay kiddo, let me explain what disappearing quorum means. Imagine you and your friends have a secret club where you make important decisions together. To make sure the decisions are fair, you all agree that at least three of you need to be present for the discussion and vote. This is called a quorum.
Now, let's say your friends are busy and can't show up for the meeting. You wait and wait, but nobody comes. Suddenly, you realize that there are only two of you left – you and your best friend. Because there are not enough members present, you can't make any decisions, and your secret club can't do anything until there is a quorum again. This is what we call a disappearing quorum, because the quorum (the minimum number of people needed) disappeared.
In the context of more grown up things, like politics or business, disappearing quorum can be a big problem because it means important decisions can't be made. That's why it's important for everyone to show up and participate if they want their voice to be heard.