A fractional rig is like a really tall stick that helps a boat go fast.
Imagine you have a toy boat, and you put a really tall stick in the middle of it that goes up really high. At the top of the stick, you attach a string with a big piece of cloth on it, called a sail. When the wind blows, it makes the sail puff up like a balloon, and the boat moves forward.
But if the stick is too heavy, or the sail is too big, the boat might tip over or go too fast and be hard to control. So, people who build bigger and fancier boats use something called a fractional rig.
A fractional rig is like having two sticks instead of one. There is a tall stick in the middle like before, but it's not as tall as it was before. This stick has a string attached to it that holds up a smaller stick that goes even higher. The sail is then attached to this smaller stick.
With a fractional rig, the sail can be made bigger or smaller depending on how much wind there is. This means the boat can go faster or slower or be easier to control. It's like having gears on a bike that make it easier or harder to pedal.
So, a fractional rig is like having two sticks that make the boat go faster, but also give you more control over how fast it goes.