There should be a .env file in the root directory of the project. If there isn't copy .env.example and name it .env. Depending on the project (craft/wordpress/static) you should see different variables that are needed.
The most important and only required variables to start are:
ENVIRONMENT="dev"
SITE_NAME="Project Name"
WEB_ROOT="/web"
TEMPLATE_DIR="/templates"
GENERATE_LEGACY="false"
DEFAULT_SITE_URL="http://project-name.test"
enviromentdev|development # Used for development (BrowserSync, source maps, live reload, etc)
production|live # Used on production servers (minify/gzip, dynamic imports, file spliting)
stage|staging # Used on staging server (file spliting, source maps)
SITE_NAMEThis variable is to defined the name of the project. This is used in different places depending on the type of project (craft/wordpress/static).
WEB_ROOT - Where the server accesses your app. This can change depending on the type of project:
/web/wp-content/webTEMPLATE_DIR - This is where you add your template or HTML files. These changes based on the type of project.
/templates/wp-content/web or where ever php/html files live.
GENERATE_LEGACY - This a Boolean value, and tell Webpack to generate a legacy version of the JS assets so older browsers use ES6+
DEFAULT_SITE_URL - This is the site URL being used to view the site.composer i Install all dependencies to run.