Let's think of a two different methods to learn how to skateboard
One way to learn how to skateboard is to purchase a skateboard, new or used, and practice riding it. Once you feel comfortable riding, you can begin practicing tricks. This would be considered a "self-taught" method of learning how to ride a skateboard. Another method would be "instructional." Instructional method of learning to skateboard would include formal training from an expert or someone proficient in skateboarding. This person or people would help accelerate your knowledge by giving you tips about how to execute riding a skateboard and doing tricks.