Now that we have ES6 modules in TypeScript, we should probably move towards a cleaner separation in the module types.

In truth, "internal modules" have been a bit of confusion for developers new to TypeScript. They're much closer to what most people would call a namespace.

Likewise, "external modules" in JS speak really just are modules now.

Let's move to a simpler explanation and have namespaces and modules be more separate. We'd still support the previous syntax, but this would mean introducing a new keyword called 'namespace' that was a bit easier to read and doesn't conflict with ES6 terminology.

Before:

module Math {
    export function add(x, y) { ... }
}

After:

namespace Math {
    export function add(x, y) { ... }
}