The person who built it seems to have been concerned with ensuring it is stable sideways for some reason, meaning that what is on top of the wall should not move to the right or left in the figure. It might also be that the posts bear a heavy load and the braces are there to prevent them from bending. Or perhaps they just wanted the wall to be sturdy. However, to know if it has a load-bearing function, one must examine what is on top of the wall. In this case, it is probably safest to also examine what is on the side to ensure there is nothing that can tip over there.