Pivotal Cloud Foundry Developer Certification - Cloud Foundry Overview - environment variables

Why does Cloud Foundry rely on environment-variables? Can you manage environment-variables manually? If so how? Can you name two predefined environment-variables available to any application?

Environment variables are the means by which the Cloud Foundry (CF) runtime communicates with a deployed application about its environment. 

To view environment variables use 'cf env APP-NAME' command. The 'cf env' command displays the following environment variables:

• The VCAP_APPLICATION and VCAP_SERVICES variables provided in the container environment
• The user-provided variables set using the 'cf set-env' command

For more details refer environment-variables