An hourglass corset is a special kind of clothing that can help change the shape of the person who wears it. It's called an "hourglass" corset because it can make someone's body look like an hourglass shape, which means that the person looks wider on the top and bottom, and smaller in the middle.
Like a regular corset, it is made of strong fabric that is laced up tightly around the person's waist. When a person wears an hourglass corset, it can push the upper and lower parts of their body outwards, while it pulls their waist inwards, making the waist look smaller.
For example, imagine you have a balloon. If you squeeze the balloon in the middle, it will get wider on the top and bottom. That's kind of like what happens when someone wears an hourglass corset - it can make their body look wider on the top and bottom, but only if it is laced up tightly to make the waist appear smaller.
Some people use hourglass corsets to help train their waist to be smaller over time. However, it's important to remember that using a corset in this way can be dangerous if done improperly. It's always best to talk to a doctor or professional before using an hourglass corset.