Can anyone explain the difference to me, it seems they are the same thing ?

OBW does not have any setting squares or triangles.
It used the Stack and Wack method to cut the triangles.
I have done a Stack and Wack hexagon quilt, where I sewed triangles on two opposite sides to form a diamond shape.
I have also done 8-pointed stars with the Stack and Wack in various sizes. I am sewing the blocks into a jacket.

They usually have a different amount of pieces per block and shapes too.

OBW are sewn together, with no additional pieces added. These are all hexagon shaped blocks.
S&W can be different shapes within the block and usually have corner pieces added to them to make them square. :D:D:D

this question comes up a lot and you all are so quick to find answer