The moment of inertia is like the twistiness of an object when it moves.
When you're on a spinning ride at a carnival, you might notice that some things are harder to spin than others. A big, heavy ball might be hard to make spin as fast as a small, light toy. This is because of something called the moment of inertia.
Imagine holding a pencil and spinning it like a drumstick. The heaviest part of the pencil is the eraser end, so it takes more force to make that end spin. That means it has a higher moment of inertia than the other end.
Now imagine doing the same thing with a weighted hula hoop. The more weight there is in the hoop, the more force it takes to make it spin. This means it has a higher moment of inertia than a lighter hula hoop.
The moment of inertia factor is a way of measuring how twisty an object is. Objects with a higher moment of inertia take more force to spin or move, while objects with a lower moment of inertia are easier to spin or move. It's like a measure of how much effort is needed to make something twist or rotate.