Nothing in Judaism is random. Many have a custom to use a Challah that is six-braided. The reason for this is to remember the special bread that was placed on the table in the Temple every Shabbat. This was miraculous bread that stayed fresh the entire week until it was replaced the next Shabbat. Altogether there were 12 of these “Show Breads.” So, we too place on our table two Challas each of them with 6 braids reminding us of that special bread.
There are some Chassidic Rebbes that actually put 12 full Challas on their Shabbat table, which might be a little much for us so we’ll just stick to the two six-braided ones…