GitHub added a new feature, Topics, which allows repo admins to tag their repositories. Topics can be things such as the purpose, language, platform, subject area, or anything else that you think might be useful as a classification.
Topics appear right below the repo’s description on the repository’s main page.
Topics allow users to more easily find repositories to use and contribute to by allowing for searches by these tags. You can perform a topic search by using the topic keyword. For example, the following would be used to search for repositories with “react” as a topic:
GitHub uses machine learning to analyze public repositories in order to provide topic suggestions. GitHub doesn’t perform this analysis on private repositories. While both public and private repositories can have topics, you will only see private repositories that you have access to when searching by topic.
If you are a repo administrator, you can classify the repository by clicking “Add Topics” under the repository description. Once you have at least one topic associated with a repository, the option becomes “Manage topics”, and allows you to delete existing topics as well as add new ones.