These are night splints or braces that you wear at night that are supposed to correct bunions. There is certainly debate and divided opinion if they actually do that or not.
A lot of force creates a bunion during the daytime. This force comes from the biomechanics and from the shoe. The force coming from a bunion corrector during the night is not only expected to overcome that force, but actually reverse the process, so you can see why opinion is so divided on that.
The actual research done on this is very limited with only one study showing that it makes only a small difference after a month's use. There is nothing on the long term use of the device and even if that small improvement is sustained over the longer term.
Even if they do not lead to much of an improvement in the alignment of the toe, they do appear to still be very helpful at keeping the joint mobile and flexible and that is a good thing.