Gatsby is a blazing-fast static site generator for React.
Site configuration options for a Gatsby site are placed in a file at the root of the project folder called gatsby-config.js.
It is usually used to set up siteMetadata and plugins. There are some commonly used plugins. gatsby-source-filesystem -- A Gatsby source plugin for sourcing data into your Gatsby application from your local filesystem. gatsby-transformer-remark -- a plugin parses Markdown files using Remark.
We can make use of Gatsby node API in the gatsby-node.js file. Two most common use case are creating custom pages driven by GraphQL data and adding new nodes or fields to GraphQL.