diaspora* is a Federated Distributed Social Networking server. Your social networking data stays with you on your own pod (server), while your contacts on other diaspora* pods will be able to connect with you using a user ids which are similar to email ids. diaspora* also allows users to connect to their friends on other federated and non-federated social networks. This means that you can start posting using diaspora* right away without waiting for your friends on Facebook or Twitter to make the shift.
Note: diaspora* is available in FreedomBox starting with Plinth version 0.15. Currently it is only available in the "contrib" repository.
diaspora* works a lot like email. It relies on a push model, which means that when you make a post or comment, the content will be pushed to all the pods of the intended recipients. When your contacts try to see your feed, they are seeing the content in the database of their own pods, not fetching it from your pod. This saves a lot of network bandwidth.
diaspora* will be available on the subdomain diaspora on FreedomBox unlike other applications which will are on paths. This is because the domain name is included in the user id. Diaspora's web interface will be served from the FreedomBox at https://diaspora.<freedombox-url>
Be careful while setting the domain name for your FreedomBox. diaspora* currently doesn't support migrating data to a new domain name. So, pods will no longer be able to push data intended for the old domain if you change the domain name of your FreedomBox.
Though there are some third party mobile apps available for diaspora*, it is recommended to access your pod's web client through the browser on your mobile device.
Read more about diaspora* on their official wiki