Hi Stephanie, these are from causal loop mapping. An R means a reinforcing loop and a B means a balancing loop, they describe the effect on the wider system. The S and the O are sometimes also shown as + or – but basically S or + shows where the effect of one thing has the same effect on the next thing in the system, so same/same e.g more sun leads to more ice cream. O or – means it has the opposite effect on the next thing in the loop e.g more rain leads to less ice cream. Does that make sense?