Deployment
For both, backend, and frontend, automatic deployment is activated. This means, when the main branch of each repository is updated - by merging some code, the new code is automaticly deployed to the server at https://puzzle.social. So new features are available instantly.
Pull Request
When you check out the code, and make some changes (for example implementing a new feature, or fixing a bug), you can push your changes back to GitHub, and create a pull request. Every other person participating in the project, can easily check out your code, and test it locally. (does it work? does it look good? Is the code clean?) After doing so, the pull request is approved, and merged back into the main branch. This is, when automatic deployment is dispatched. Can't wait to see how new features are developed by the community.
Next
Read the next chapter, to learn about this documentaion.