Confluence is a popular Enterprise Wiki and collaboration platform by Atlassian. It is available as a cloud service as well as a downloadble package for self-hosting. It is a commercial platform, however, for up to 10 users the cloud service is free and the downloadable package cost $10 (one-time).
The cloud service and the self-hosted version differ a lot in features and user interface. I am involved in the use and administration of both and would like to share tips and tricks about it in this documentation.