How many Action Points (AP) you get to spend each turn in battle. Each action in combat (moving, shooting, skill usage etc.) costs AP. More is better.
Ranged Hit Bonus
The Ranged Hit Bonus will be added to a weapons Base Hit Chance for your Total Hit Chance. In addition to weapons, as you level up your combat skills, your chance to inflict a Critical Hit will increase.
The Critical Hit Chance Bonus will be added to a weapons Base Critical Hit Chance for your Total Critical Hit Chance. In addition to weapons, as you level up your combat skills your chance to inflict a Critical Hit will increase.
How often your turn comes up in combat. The higher your Combat Initiative, the more often your Ranger will get a turn in combat. Each enemy has their own Combat Initiative or turn order.
Chance to Evade
Evasion allows you to decrease the Chance to Hit from all enemy attacks.
How much Constitution (CON) or hit points you have. When your current CON reaches 0, you will go unconscious. An unconscious (or worse) Ranger will require a Surgeon to bring them back to their feet. If your health deteriorates beyond unconscious, you are on your way to death.
The amount of distance you can cover per Action Point, in combat. Increasing your combat speed will allow you to travel much further (while in combat) than a Ranger with an equal number of action points, but a lower combat speed.
On leveling up, you will get a # of Skill Points to distribute in your skills. This is how many Skill Points you will receive during each promotion.
The Maximum Carry Weight determines how many items you can carry before becoming encumbered. When you reach 100% or more of your Maximum Carry Weight, you will become encumbered and unable to move. Dropping heavy items in the world or trading them to other Rangers is your best bet to get moving again.
CON per Level
The amount of Constitution (CON) that will be added to your maximum Constitution each time you level up. A Ranger with a higher CON per Level will be able to take more damage as they progress in rank.