The `preview` command starts a server to preview your Nuxt application after running the `build` command. The `start` command is an alias for `preview`. When running your application in production refer to the [Deployment section](/docs/getting-started/deployment).
For convenience, in preview mode, your [`.env`](/docs/guide/directory-structure/env) file will be loaded into `process.env`. (However, in production you will need to ensure your environment variables are set yourself.)