1.**`.prettierrc`**: This is a configuration file for [Prettier](https://prettier.io/). Prettier is a tool to help keep the formatting of your code consistent.
2.**`gatsby-browser.js`**: This file is where Gatsby expects to find any usage of the [Gatsby browser APIs](https://www.gatsbyjs.com/docs/browser-apis/) (if any). These allow customization/extension of default Gatsby settings affecting the browser.
3.**`gatsby-config.js`**: This is the main configuration file for a Gatsby site. This is where you can specify information about your site (metadata) like the site title and description, which Gatsby plugins you’d like to include, etc. (Check out the [config docs](https://www.gatsbyjs.com/docs/gatsby-config/) for more detail).
4.**`gatsby-node.js`**: This file is where Gatsby expects to find any usage of the [Gatsby Node APIs](https://www.gatsbyjs.com/docs/node-apis/) (if any). These allow customization/extension of default Gatsby settings affecting pieces of the site build process.
5.**`gatsby-ssr.js`**: This file is where Gatsby expects to find any usage of the [Gatsby server-side rendering APIs](https://www.gatsbyjs.com/docs/ssr-apis/) (if any). These allow customization of default Gatsby settings affecting server-side rendering.