A tutu is a piece of clothing that ballerinas wear when they're dancing. It looks like a big, fluffy skirt that's made out of layers and layers of fabric called tulle. Tulle is kind of like a thin netting material that can be sewn together to create a puffy, bouncy effect.
The tutu usually comes in two different styles: the classical tutu and the romantic tutu. The classical tutu is the shorter one that sticks out straight from a ballerina's waist, while the romantic tutu is the longer one that falls down to a ballerina's knees.
To make a tutu, you need to start with a waistband, usually made of elastic. Then, you take long strips of tulle and sew them onto the waistband one by one. The more tulle you add, the fuller and fluffier the tutu will become. Some tutus also have decorations, like sequins or jewels, to make them even more sparkly and pretty.
When a ballerina wears a tutu, they usually also wear ballet shoes and tights to complete the look. They use their tutu to help them dance and twirl around, and it looks super cool when they spin really fast because the tutu spins around with them.
So that's a tutu--a special skirt made of tulle that ballerinas wear when they're dancing to help them look beautiful and graceful.