After a pull request has been opened, you can review and discuss the set of proposed changes.
Reviewing proposed changes in a pull request
In a pull request, you can review and discuss commits, changed files, and the differences (or "diff") between the files in the base and compare branches.
Commenting on a pull request
After you open a pull request in a repository, collaborators or team members can comment on the comparison of files between the two specified branches, or leave general comments on the project as a whole.
Checking out pull requests locally
When someone sends you a pull request from a fork or branch of your repository, you may want to merge it locally to resolve a merge conflict or to test and verify the changes on your local computer before merging on GitHub.