Mechs have several characteristics; they have five stats, any number of appropriate Abilities, and six to ten Attacks.
HIT POINTS, usually abbreviated HP and also called health, represents how long it takes to destroy a robot. Unlike almost all other stats (except SP and EN), HP has both a current and a maximum value. All damage the mech takes is subtracted from current HP, and when it reaches or passes 0, the mech is out of the fight due to damage. See Hit Points for details and an example chart.
HP ranges from 5000 to 15000.
ENERGY, usually abbreviated EN, is the internal battery or engine power of a robot. Like HP, it has a current and maximum value. EN is used to power certain attacks that come from inside the mech and represent a notable drain on its power. If you don't have enough EN, you can't use these weapons.
EN ranges from 50 to 250. It is possible that a mech has no use for Energy whatsoever. In this case, it will be set to the lowest number, 50 EN. Humans who are capable of fighting against robots, however, have 0 EN, as they do not have a battery or engine.
ARMOR is used to represent how hard your robot is to hurt. It is used along with the pilot statistic Defense to calculate how much less damage you take from a given attack; a high Defense will partially make up for an average Armor and vice versa. See Armor for details and an example chart.
Armor ranges from 1000 on a totally unarmoured mech to 3000 to a perfect defense.
MOBILITY is a representation of how mobile and agile a robot is. It is used both with Accuracy to determine how easy it is for a pilot to hit, and with Evasion to determine how easy it is to evade. Mobile mechs respond more quickly to the pilot's commands and are both more agile and dextrous, while low Mobility mechs may be blocky or awkward to control. See Mobility for details and an example chart.
Mobility ranges from 1-100. Very few mechs have under 35 or 40 Mobility unless they can neither move themselves nor their weapons.
SIZE represents how big a mech is. See Size for details and an example chart.