Skills are an important part of any MMORPG, and that's the case in this game. Kirito has the option to use a total of 10 different weapons in the game (not counting the sword and shield combo), and each one of those weapons has a set of skills and skill level associated with it. As you use each weapon, the skill level will increase and you will earn Skill Points.
For every 10 points you earn in a skill level, you will get a single Skill Point. On the skill tree, you will notice that some skills are required in order to learn others. You will also see that each skill node on the tree has skills within it, which are divided into Battle Skills and Passive Skills. Below is a picture of the entirety of the skill tree, as shown in-game.
