[quote=@Sublimation]
<Snipped quote by Turboshitter>

What the skills actually do. Like what would Berserker's Mad Enhancement do, or does it even exist in here at all, what would magic resistance do since it completely depends on ranks for canceling out magic under certain verses, etc.
[/quote]

Oh boy. You have just invited me to unleash my full Type-MOON nerdiness on you. WARNING: MAJOR FUCKING MAGI-BABBLE RANT AHEAD.

Mad Enhancement of C-rank and above applies an extra stat buff beyond what the Servant's base stats are at the cost of robbing them of their sanity. At C-rank the gains are minimal and the Servant only loses its ability to speak and sustain patterns of complex thought (Frankenstein's monster, which has a D-rank, is actually capable of basic speech and can think about as well as a child or someone who's mentally handicapped). At B and A rank the Servant becomes increasingly insane, more like a mechanical engine of rage than a person, and they will even begin disobeying non-Command Spell orders from their Master (Heracles and Lu Bu being unusually obedient has its own story behind it). In exchange, A and B rank Mad Enhancement grants additional rank-ups in all stats, whereas C-rank only increases physical parameters while leaving Mana and Luck untouched. 

For example, here are the stats of Heracles and Lu Bu, before and after Mad Enhancement:

Heracles (B-rank):

Strength: A -> A+
Endurance: B -> A
Agility: B -> A
Mana: B -> A
Luck: C -> B

Lu Bu (A-rank):

Strength: B -> A+
Endurance: B -> A+
Agility: C -> B+
Mana: D -> C+
Luck: D -> C+

Mad Enhancement can be turned on and off at will (some Masters like Illya just [i]choose[/i] to keep their Servant permanently mad), but the stat boost no longer applies if it's turned off.

As for Magic Resistance, it does what it says i.e. resists magic. Since most RPs don't go into detail about the rankings of various magics outside of the Servant system, all you really need to know is that C-rank allows you to no-sell most modern magic besides what many mages would consider trump cards (High Thuamaturgy and Greater Rituals), B-rank makes you able to resist even those with minimal damage, and A-rank means you are pretty much the God-King of anti-magic and that you're untouchable to anyone without Servant-level magic. Basically in the modern age they'd be considered a magus killer, and the only magic capable of affecting them comes from Caster (and even that's not always a given, hence why Magic Resistance is the reason Casters are usually considered the worst class in the Holy Grail War).