I have been reading the different sites on simmer,and read from one site that said a simmer is a simmer,nothing else.Not boiling ,but with little bubbles. If this is true then why do recipes have rapid simmer,medium simmer? Is there different simmers? I found when look up simmer,first bring to a boil than down to simmer......simmer just bubbles ,but nothing on rapid simmer,medium simmer,or even gentle simmer. only recipes that they say the above.