docs: explain how environment variables work in production (#27189)

docs/2.guide/2.directory-structure/2.env.md

@@ -33,11 +33,25 @@ npx nuxi dev --dotenv .env.local
 
 When updating `.env` in development mode, the Nuxt instance is automatically restarted to apply new values to the `process.env`.
 
-## Production Preview
+## Production
 
 **After your server is built**, you are responsible for setting environment variables when you run the server.
 
-Your `.env` file will not be read at this point. How you do this is different for every environment.
+Your `.env` files will not be read at this point. How you do this is different for every environment.
+
+This design decision was made to ensure compatibility across various deployment environments, some of which may not have a traditional file system available, such as serverless platforms or edge networks like Cloudflare Workers.
+
+Since `.env` files are not used in production, you must explicitly set environment variables using the tools and methods provided by your hosting environment. Here are some common approaches:
+
+* You can pass the environment variables as arguments using the terminal:
+
+   `$ DATABASE_HOST=mydatabaseconnectionstring node .output/server/index.mjs`
+
+* You can set environment variables in shell configuration files like `.bashrc` or `.profile`.
+
+* Many cloud service providers, such as Vercel, Netlify, and AWS, provide interfaces for setting environment variables via their dashboards, CLI tools or configuration files.
+
+## Production Preview
 
 For local production preview purpose, we recommend using [`nuxi preview`](/docs/api/commands/preview) since using this command, the `.env` file will be loaded into `process.env` for convenience. Note that this command requires dependencies to be installed in the package directory.