These are splints or braces that you wear at night that are supposed to correct bunions. At least that is what the marketing hype claims.
Questions often get asked in forums if they work or not (see here and here). Despite how widely these are used, there is very little research been done on them to determine if they do actually make a difference or not. There are plenty of un-scientific claims for them and plenty of before and after photos (that are easy to fake).
There has been some research done on them that has shown, that yes they do work somewhat. After one month of use they did improve the ankle of the big toe by a few degrees. It could be debated if that is enough to actually make a difference and if that there would be more improvement if they were worn for longer than one month.
Even if that research does show the help, the foot does get put back into the shoe that will push the toe in the opposite direction, so any good is going to be undone over time.
There is, however, some commentary and clinical experience that even if they do not “correct” the bunion, they will help keep the toe mobile and that mobility can only be a positive thing for the joint.