Nice System!.
Another name for the Strike Tank is the "Hot Liquor Tank" or HLT.
The Cooler is the Mash Tun. Steeping the grains in there in hot water at controlled temps is called "mashing". This allows the enzymes that are naturally present in the grain to kick in and work their magic convert the starches in the grains into sugar.
Temp is really important here, which is why a cooler is nice because the insulation helps keep the temp steady. Different enzymes are active at different temps. Some are good at breaking up proteins so that you get a nice head on the beer (among other things). Others are good at breaking up the starches. In particular, there are 2 enzymes, called Alpha and Beta Amylase, which act on the starch chains.
Alpha Amylase can pretty much chop the starches at random, so you get lots of dextrins of various sizes, both short and medium chained sugars. Beta amylase works on the ends of the starches, like pac-man, creating lots of little sugars and thereby creating primarily a very fermentable wort. The beta is most active from about 131F to about 148F or so. The Alpha amylase is most active from about 152F to about 158F.
Remember, those temperature bands are where they are MOST active, but they are also active in the nearby temps around those bands. So, if you hit that temperature slot in between the two enzymes' temperature ranges, you allow BOTH enzymes to work together to get a wort that has a good mix of dextrins and sugars, so you end up with a medium bodied beer. By going a bit higher temp, you favor Alpha so you get a thicker beer, since there are more longer chain sugars. By going a little lower, you favor Beta amylase, so you get fewer chunks and more simple, fermentable sugars, and hence a thinner beer.
Basically, you can "design" how the beer ends up by simple little variations like this.
After mashing, you rinse or "sparge" the grains to get the sugars out of the mash and into
the kettle.
Boiling helps stabilize the wort and sanitize it, among a few other things.
Hops are added at different times during the boil to provide different effects. When hops are first added to the boil, the hot water helps bring out a lot of volatile aroma. As they boil longer, more of the aroma is driven off and you extract more hop flavor out of the hops. If you leave them in even longer, even the flavors are volatized out, and the alpha acids that are in the hops are converted into iso-alpha acids which provide bitterness to the beer. So, by adding different amounts of hops early, mid-time, and very late in the boil, you can vary the mix of bitterness, flavor, and aroma you get in the finished product. Different varieties of hops have different bitterness, flavor, and aroma characteristics, and as such they can greatly affect the final flavor/aroma profile of the beer.
Maybe someone else can chime in on yeast and fermentation.
HTH-
