Arduin Eternal took a different path in defining how to gain experience from the systems before.
From its pages:
Role-players believe a character's advancement should be based on how well that character is role-played as well as actual game-play experience. Contrasting this type of thinking is the adventurer player type that believes a character's advancement should be based solely on actions taken by that character during the game. In short, the role-players believe any form of advancement should be awarded for playing totally in character (among other things) while the adventurers believe that a character should only advance from game system methods of reward. Truly the difference in opinion comes from the fact that role-players think that they contribute more to a game than just rolling dice and so should be rewarded for any acting ability, no matter how bad. The adventurers, on the other hand, think that it is unrealistic for a character to gain any advancement based on the actions (or lack thereof) of that character's player; they don't believe that any acting ability should be rewarded, no matter how good.
The real truth lies in a balance between the two spectrum by taking the best attributes of each approach. Arduin Eternal makes this leap by looking at experience using dual method of improvement. The first method of improvement is via a Skill Advancement and Development activity that occurs following each game session. Skill Advancement and Development is not a reflection of training but intuitive jumps, application of previous knowledge, tasks, and maneuvers and just putting together a concept you mentally understood but did not practically comprehend until circumstances thrust you into the right mold to figure it out. Nightly Skill Advancement and Development checks provide immediate and necessary feedback to the player and give a sense of improvement with your character. The second method is through Experience or EPS. EPS is a slice of time, resources, knowledge, experience and dedication. EPS are also a measure of how much your character has learned, practiced, grown knowledgeable or just progressed personally. EPS are given along a point defined by the GM, usually at the end of a specific story arc, expedition or time frame.
Arduin Eternal, as you read above split experience into two activities, one that happened as an active byproduct of game play and another that was more strategically driven by the player as an after game play activity. Its more complex than the previous systems but it fit the more complex system that had evolved, being as granular as the system had become.
This method of experience allows for strong non-holistic improvement, since you mark skills, saves, defenses and other improvement possible items and they have a chance to get better based off their use. At the same time, each session gives you an amount of experience you can invest: either in the same items or to get new capabilities, what AE called secrets. About 20% of secrets are packages of bonuses the rest are new abilities, like to strike at the beginning of a melee, attack a person's ability to move power, talk to spirits, castigate your enemies, inveigle people socially and so on.
In the pursuit of an average game, a person would see 1-18 points of advancement in improvement items (higher at lower skill levels) and earn 1 or more EPS to either turn into the same or to get a secret, i.e. a new ability.