An environment refers to a branch of a site or application. For example maybe you are working on a new update for a clients website. Before deploying you want to show them what you worked on. Generally this is called a staging or acceptance environment.
This version of the website is probably ahead of what is currently live for the public to see. Generally this environment is called master or production.
Learn more about branching & deploying in the workflow strategy article >
Create new environment
First off the environment needs a branch. This can be anything you like but keep in mind that this is influences deploys. When a new commit is pushed Forest will start builds if the branch name of the commit matches an environment.
Now create or choose a blueprint to work with.
Continue setting up a blueprint >