The goal of a language track on Exercism is to give people a way to achieve a high level of fluency at a low level of proficiency.
We're aiming for fluency in the syntax, idioms, and the standard library of the language.
The Language Hunters describe fluency as
What you can say when you're woken up in the middle of the night with a flashlight in your face.
This is distinct from the concept of proficiency, which is not about ease, but about degree.
They describe four levels of proficiency:
You can have the ability to perform at a level without being able to do so under stress. Proficiency does not automatically mean fluency.
While these were defined in the context of human languages, they map quite well to programming languages.
Within this framework, with Exercism we're aiming for a high degree of fluency at a level 2 proficiency. This bridges the gap between "Hello, World" and productivity.
Being fluent at this basic level lets people put all of their focus on thinking at a higher, more useful level. It also puts them in a good position to consume the existing resources and documentation for the language.