All pilots have six primary statistics, ranked from 1-100. Most player characters have 40-50 in their bad skills and 70-80 in their high skills; anything over 90 is extremely rare and means you are approaching the best in your skill.
ACCURACY is the measure of how well the pilot can hit and damage an opponent. Pilots with very low Accuracy might be clumsy, bad at targetting, or just be unlucky. Very high accuracy pilots know where an enemy is going before they do.
EVASION is the ability of a pilot not to be hit. Pilots with low Evasion might have bad reaction time, a tendency to rush into attacks like a berserker, or be used to piloting slow mechs. High Evasion pilots have an uncanny ability to stay out of the way, and may actually be prescient.
DEFENSE is the skill of a pilot to avoid serious damage. Pilots with low Defense don't know how to roll with a blow, or can't keep their mech responding properly after it's hit. On the other hand, those with high Defense can shrug off even extremely powerful weapons to an extent and keep on going.
MELEE and RANGED are the ability of a pilot to do damage with a certain class of weapon. A high Melee character might have unparalleled skill with a beam sword, while a high Ranged character might be a sniper, a heavy weapons specialist, or just very good at making their weapons go the extra mile. Having a high Melee or Ranged also improves your aim slightly with that type of weapon, although Accuracy is significantly more useful.
There is no difference between Melee and Ranged except what class of weapon it affects.
SPIRIT is the catch-all term for a pilot's talent and ability to be exceptional. It does this by allowing access to Spirit Commands, or temporary effects that add bonuses or effects that don't usually exist. This stat requires no IC training and in fact no IC training for Spirit really exists. High Spirit characters might be exceptionally skilled, prone to flashes of insight, or the luckiest person in the world. Low Spirit characters may be otherwise talented but unexceptional; they don't stand out in combat. Generic NPC soldiers have very low Spirit; it tends to be the province of PCs.
Pilots also have two derived stats, which are SP (Spirit Points, what are actually spent to use Spirit Commands) and Will. For information on Spirit Points, see 'news spirit commands'. For information on Will, see 'news combat will'.