Skill Points are used for buying Skill in Borderlands 3. These Skills will make your Vault Hunter a lot more powerful, and range from passive effects (such as gain + X % dag), on-kill effects (gain X health each time you kill an enemy) to more active effects. You definitely want to use all the Skill Points you get in your Skill Tree, but how exactly do you get more Skill Points?
The method for getting new Skill Points is to level up. Each time you reach a new level, you are awarded with a single new Skill Point. There is currently no other method to getting Skill Points in Borderlands 3, so go out there and grind EXP until you level up to get it.