Actually FROSTR very simple to understand , just like your home key in pairs then you share it or put it in 3 different place , you make 3 copy of your key home then put one in the A place then 2nd key on B place then 3 key in C place. Whenever one of your identify lost .. then you can recover by the use of other share key you have .
To prevent misused then the one who stole your key can not operate without the other share .