The Learning Curve Is S-Shaped
The learning curve is the relationship between proficiency and experience (i.e. ability as a function of time spent learning). In other words, how long it takes to acquire new skills or knowledge.
For most skills, the learning curve is S-shaped and has three stages:
When you first start learning a skill, you start off at the low end of the learning curve, where your ability increases at a slower rate per unit time. This is often perceived as a barrier to learning due to the time invested not resulting in significant increases in ability. This is where most people give up.
Eventually, some kind of breakthrough occurs, and you get past the initial learning barrier. You reach the middle of the learning curve, where your ability increases at a faster rate per unit time than in the first stage - often at an increasing rate.
As you gain more experience and approach the higher end of the learning curve, the progress that you make per unit time begins to decrease as you experience diminishing returns. You eventually require significantly more time to improve your ability by the same amount than you did before as you approach the top percentile.
Understanding the three stages of the learning curve is important because it provides a roadmap of expectations on what is achievable at each stage and the time required for each stage. It allows you to better approach and optimize each stage.