Contribution guidelines explains how to contribute to a project:
GitHub will show a link to contributing guidelines on the new pull request page.
Code of Conduct is document that describes what behavior is acceptable for project’s participants. They will feel safer when they know that maintainers won’t tolerate bad behavior.
GitHub has a wizard to help you choose and add a code of conduct to your project.
Read more about code of conducts in the GitHub open source guide.
GitHub doesn’t have enough tools to ensure that issues and pull request are of good quality. Issue and pull request templates are text files that GitHub shows as a default text when someone creates an issue or a pull request.
Issue and pull requests are discussed in greater details in the Processes chapter.