With topics, you can explore repositories in a particular subject area, find projects to contribute to, and discover new solutions to a specific problem.
Topics appear on the main page of a repository. You can click a topic name to see related topics and a list of other repositories classified with that topic.
You can contribute to GitHub's set of featured topics in the github/explore repository.
Repository admins can add any topics they'd like to a repository. Helpful topics to classify a repository include the repository's intended purpose, subject area, community, or language. Additionally, GitHub analyzes public repository content and generates suggested topics that repository admins can accept or reject. Private repository content is not analyzed and does not receive topic suggestions.
Public and private repositories can have topics, although you will only see private repositories that you have access to in topic search results.
You can search for repositories that are associated with a particular topic. For more information, see "Searching repositories."