Nutshell: The big, blue button will soon say "Publish page" instead of "Save page", because when you click it, the contents get published on the internet.
I apologize for cross-posting this to the GLAM and Education lists:
A long-requested change to the "Save" button may finally happen towards the end of March. This is a button that anyone leading a workshop about editing is going to talk about, so I wanted to make sure that you didn't get surprised by this change.
Last year, the WMF looked into an old request to clarify the language on the "Save" button, which confuses some new contributors. The main problem is that it is unclear whether "Save" means "save a private copy" (as it does on most websites these days) or "irrevocably post this to the internet". This confusion apparently explains a few unwanted behaviors, such as editors who save the page ("just to be safe") before previewing their changes.
There are some other reasons behind to do this: It creates some inconsistency in the interface, as some things (e.g., Special:Preferences) get saved but kept private, while other things (e.g., normal wiki pages) get saved and immediately published. It is also difficult to translate the label into some languages, as the word has multiple possible translations in some languages.
The plan, therefore, is to change "Save" to "Publish". Instead of the big blue[1] button saying "Save page" (for a new page) or "Save changes" (when you edit an existing page), the button will instead say "Publish page" or "Publish changes".
The upside to this small change is that new contributors will understand that all of their edits go to the public immediately.[2] The downside is that all of the documentation and help pages is going to be out of date.
This plan was announced on the wikis last August, and is tentatively scheduled for sometime in March. I hope that this extra note will keep you from getting surprised in front of a group and give you enough time to update any handouts that you might be using in the future.
Relevant links:
[1] The color of this button in all of the older wikitext editors will be changing this week. It's going to be big and blue.
[2] This is true even when the wiki is using FlaggedRevisions or PendingChanges, because the un-accepted changes can be seen by the general public from the history page or from &oldid URLs, regardless of whether the revision has been accepted.