A quasi-unmixed ring is like a special type of toy box that only has certain types of toys in it. Imagine you have a toy box filled with different types of toys like action figures, stuffed animals, and puzzles.
But in a quasi-unmixed toy box, all the toys are the same type. So imagine if you had a toy box with only action figures.
Now let's say you have another toy box with action figures and puzzles mixed together. This toy box would not be a quasi-unmixed toy box because it has different types of toys in it.
Just like in math, a quasi-unmixed ring is a type of set where all the elements are the same type, and there are no other types of elements mixed in.