Nowadays a beged (i.e. garment) with tzitzis has 4 strings on each corner that are then tied in such a way so it comes out as 8 strings altogether hanging down. It is then connected to the beged with 5 knots and a number of times wrapped around between each knot (with various minhagim (i.e. customs) on how to tie the tzitzis exactly.)
This is what we do now, however M'Doraisa (i.e. Biblically) what does a beged with tzitzis look like? How many strings would satisfy the requirement M'Doraisa? Would one string (tied in a single knot -- kesher elyon d'oraisa (the top kesher in min hatorah) and hanging down as 2 fulfill it? Do we need 4 (doubled to 8) strings M'Doraisa?