# Technical overview
# The core tech
In brief, the main technologies behind Apostrophe are:
- Node.js (opens new window): Popular server-side JavaScript runtime. We originally chose Node.js to achieve a fully-JavaScript development experience for developers. It has continued to improve over time, delivering high performance and powerful features we can use.
- Express (opens new window): Un-opinionated Node.js web framework. Express is the most widely used web framework for Node.js. Because it is simple, un-opinionated, and well-known, it was straightforward to extend it to suit Apostrophe's needs.
- MongoDB (opens new window): Secure, document-based database engine. We chose MongoDB for its fluent JavaScript-based API, its safety from "SQL injection"—style attacks, its developer-friendliness, and its support for documents with varying schemas in the same collection.
- Nunjucks (opens new window): Richly featured template language for JavaScript. Nunjucks provides tons of features, extensibility, and a syntax nearly identical to Twig, Jinja, and other Django-inspired templating languages.
# Directory structure
There are a few directories and top-level files that are especially important in Apostrophe projects. Here is a rough overview of these files and folders you will see in the official boilerplate, starter-kit-essentials.
| Folder/File | What is it? |
|---|---|
app.js | The heart of the application. This is where you tell Apostrophe what modules are in your project and set a few top-level parameters. |
/modules | All project-level modules and configuration for installed modules. |
/public | Public, static files (not managed through the CMS). Apostrophe will generate specific directories inside, but you can also use it as needed. |
/views | Template files that do not belong to any one module. Apostrophe looks for site wrapper templates here, including layout.html. |
TIP
Core module configuration is all done in a subdirectory of modules: modules/@apostrophecms. This keeps core modules organized together and out of the way, following the npm scoping pattern (opens new window).