Angular CLI build target vs environment

--environment is a key for the apps[0].environments object from .angular-cli.json

It is like a profile for the running environment (for example: local, development server, test server, CI server, stage server, production server and so on). The value of the apps[0].environments object is a file name with all settings for the environment. There you could set up backend endpoint, keys and whatever else you want. Then you could use it inside your code:

import {environment} from '@environments/environment';
const userEndPoint = `${environment.apiRoot}/user/`;

Every environment could be production (environment.production === true) or non production i.e. development (environment.production === false). This is a target which could be defined also with the next parameter:

--target is a enum of two values: development or production. It is a 'meta' flags, that set other flags:

Flag | --dev | --prod
--- | --- | ---
--aot | false | true
--environment | dev | prod
--output-hashing | media | all
--sourcemaps | true | false
--extract-css | false | true
--named-chunks   | true | false
--build-optimizer | false | true with AOT and Angular 5

--prod also sets the following non-flaggable settings:
- Adds service worker if configured in .angular-cli.json.
- Replaces process.env.NODE_ENV in modules with the production value (this is needed for some libraries, like react).
- Runs UglifyJS on the code.

from https://github.com/angular/angular-cli/wiki/build/1cf783837c392f5fadc7286e1fb28220b9a1b507#--dev-vs---prod-builds

As of Angular CLI 6, the environment option has been deprecated.

The environment option in build related commands is replaced with fileReplacements, please see the wiki for how it can be used.

The build system has been overhauled to be more easily configurable. Build configuration options have been moved to the workspace configuration file (angular.json).

A "production" configuration is created by default when you use the CLI to create the project, and you can use that configuration by specifying the --prod option.

The difference between the default development configuration and production is that the development configuration uses the CLI defaults (e.g. source maps) while the production configuration enables AOT, optimizations, etc. The --prod meta-flag targets the "production" configuration and enables the runtime production mode.

Switching to production mode makes it run faster by disabling development specific checks such as the dual change detection cycles.

The term "environment" has even been replaced with "build target" in parts of the documentation. The --target option was replaced with --configuration as early as CLI version 6 as well.