Nix is a bit like JSON + functions.

An object (called attrset in nix):

    { a = 3; b = 4; }

A list:

    [ 1 2 3 4 ];

A string:

     "hello"

A multi-line string:

    ''
      multine
      string
    ''

This defines a lambda with two arguments:

    a: b: a + b;

It's possible to pattern-match arguments. This accepts an attrset with keys a and b, and maps them to local variables:

    { a, b }: a + b;

There are some variations around that like `{ a ? 3 }:` `{ a }@attrs:` and `{ a, ... }`

One special type is the path, which has it's own literal that starts with `./`

To load a file, the `import` keyword is being used. In most cases the whole file is a big lambda function, which gets returned by the import.

Once you know that you can start reading nixpkgs and learn about the building blocks to constructs packages.