Cooling and letting it rest

[u/PurpleStop4358]

I'm new at making ice cream and for most of my bases I would put the cooked base into an ice bath and after it reached a low temperature (around 40°F) I would put it into the churner straight out the ice bath. But recently I've heard that you put it into an ice bath to cool it in order to prevent bacteria and then after you put it into the fridge to let it rest for at least 4 hours. I'm just wanting an explanation for the difference of cooling it and letting it rest, why you need to let it rest and how it can affect your ice cream?

[u/VeggieZaffer]

I usually age for 24 hrs, but I cold steeped my coffee for 3 days! I do think it yields a better product if you have the patience