A "quot scheme" is a way of talking about something that is made up of different parts. It's like if you went to a candy store and saw a big jar of gummy bears. You could say that the jar is the "quot" and the gummy bears are the "scheme" because they're what make up the jar.
In more grown-up terms, a quot scheme is a mathematical way of taking a big thing and breaking it down into smaller pieces. You might use a quot scheme to study how a group of people interact with each other, or to figure out how much money a company is making.
Basically, it's like taking a big puzzle and breaking it into smaller pieces to help you understand each part better!