Skill Levels are structure int the Base Levels that contain basic skills and two emerging branches for two different riding styles. One for Freestylers the other for Street/Flatland riders (temporarily named “extreme” until we have a better name).
The main reason for a skill in a certain level is that skills are learned in the right order (as opposed to the public believe they are sorted by difficulty). Thus the levels depend on each other and require a learner to do skills from the former level(s). That is to ensure a clever order for learning. Riders don’t need to struggle on a certain skill or overload themselves because they already learned the requirements before.
Next you should check the skills for each level:
Base Levels
Freestyle Levels
Extreme Levels
Or check out the FAQ if you have questions regarding the Skill Levels.