What are Preview Deployments?
Preview Deployments automatically build and deploy a (private) preview version of your application whenever you commit changes to your repo. The preview runs alongside your active application and helps you to quickly test changes to your code without having to deploy to a separate environment.

More Info:

• Using Preview Deployments (https://help.cloud66.com/rails/how-to-guides/deployment/preview-deployments.html)
• Setting up Preview Deployments on GitHub (https://help.cloud66.com/rails/how-to-guides/deployment/preview-deployments.html#setting-up-previews-on-github)
• cloud66.com