Write an overview of Exercism

This is a very high-level overview of the project, intended as a starting point
for people who think they might want to contribute.

docs/overview-of-exercism.md

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-*(This page needs to be written.  See [exercism/exercism.io#3253](https://github.com/exercism/exercism.io/issues/3253) for details.)*
+# Overview of Exercism
+
+Exercism—as an open source project—has two distinct parts.
+
+1. The Product
+2. The Curriculum
+
+Most open source projects are code that people incorporate into their own projects. They're tools and components used to build software: libraries and frameworks, packages and infrastructure.
+
+Exercism is unusual in the open source landscape. Exercism isn't a component or infrastructure. Exercism is an experience targeted at the end-user.
+
+If you want to follow along on the high-level goings-on on the Exercism project, watch the [discussions][] repository, and sign up for the [newsletter][].
+
+## The Product
+
+The product consists of a website and a command-line client (CLI).
+
+We are currently investing our efforts in design research and product design.
+
+While we welcome fixes and improvements to the existing site, we are taking a step back from it and doing design research from scratch. You can read more about this in the article [The Delightful Design of Exercism][design-of-exercism].
+
+## The Curriculum
+
+The curriculum is much more like a traditional open source project. It consists of many small, well-defined components, and it is a lot easier to contribute to.
+
+The goal of the curriculum is to create many small, trivial exercises. These provide lots of achievable challenges, giving people many small wins.
+
+There is a common pool of exercises which are implemented in many different programming languages.
+
+### The Common Pool
+
+An exercise is a description of a problem to solve. This description is not specific to any particular programming language or library or tool.
+
+An example is:
+
+> Determine whether or not a word is an [isogram][].
+
+You could do this on the back of a napkin, or on a whiteboard, or by writing code.
+
+There are many ways to contribute to the common pool:
+
+- fix typos
+- improve exercise descriptions
+- document edge cases
+- discuss philosophical questions
+- make up more exercises
+- define canonical data-sets to make it easier to implement the exercise
+
+The common pool is maintained in the [exercism/x-common][x-common] repository.
+
+### The Language Tracks
+
+A programming language that implements exercises from the common pool is called a _language track_.
+
+A language-specific implementation of an exercise consists of a collection of automated tests, that define the requirements of the solution.
+
+A good test suite will not mandate a particular approach, but will allow people to try many different approaches, and solve the exercise in many different ways.
+
+There are many ways to contribute to a language track, described in the document [Getting Involved in a Language Track][getting-started-track].
+
+[isogram]: https://en.wikipedia.org/wiki/Isogram
+[discussions]: https://github.com/exercism/discussions/issues
+[newsletter]: http://tinyletter.com/exercism
+[design-of-exercism]: http://tinyletter.com/exercism/letters/the-delightful-design-of-exercism
+[x-common]: https://github.com/exercism/x-common
+[getting-started-track]: /docs/getting-involved-in-a-track.md