I understand that one adds different minerals to water to achieve different types of water, which might cater to a particular style (i.e. if you're brewing a Weiss beer, you alter your water to mimic the water from a particular region of Germany).
BUT, my question is, where and when do these minerals come into play in the brewing process? Do they have an effect only in the mash (i.e. change mash efficiency), or do they effect the yeast during fermentation? I'm confused what exactly different minerals do and what part of the brewing process they affect. Sorry I can't be more specific about which minerals, but to rattle off a few calcium chloride and sodium chloride (I think... again, sorry for being vague).