The cookie dough freezes very well, as does the finished cookie. I personally prefer to freeze the cookie dough which needs only about a minute of extra baking time.  Regardless of whether you are freezing the dough or the finished cookies, make sure they are stored in an airtight container to retain freshness. When freezing the finished cookies, make sure they are completely cooled down, and for best results, leave a sheet of parchment between the layers of cookies (this is true for almost every type of finished cookie you freeze.)