Bunion correctors are splints that are supposed to hold the toe in a correct position and so correct the bunion. They are worn at night. There are plenty of before and after photos that allegedly claim they work. Many of them are fake.
The don’t really work that well. Any correction that occurs overnight is going to be undone the next day with the pressure from the shoe, so if they do “correct” anyone’s bunion, its not going to be by much. However, bunion correctors still can be helpful to manage some of the aches that occur inside the joint.
If you do want to use them, then there is nothing wrong with them, just be realistic about your expectations as to what they will achieve.