... that Bitbucket replaced Stash
Stash has been rebranded to Bitbucket Server. The bitbucket.org is usually referred as Bitbucket Cloud. Both are repository hosting tools, their basic features are quite similar (although there are differences too, e.g. Cloud can host Mercurial repositories, Server offers advanced data replication etc). Bitbucket Server runs on your own machine, Bitbucket Cloud is hosted by Atlassian.