It seems like, in Office 365, there are a few different ways for users to identify objects (files, pages, etc.) that they may want to get back to easily later. I think the first instance of this was the ability (in Office apps like Word, PowerPoint and Excel) to "Pin" a file. It would then show up in the backstage for that app in the "Pinned" tab. This was fantastic. No matter where a file was stored - in OneDrive or any SharePoint site - it was easily accessible via its native app. There was also a "Pinned" tab/section in the Office Portal (portal.office.com) where you could see ALL of your pinned docs, regardless of application...even better!
When MS renovated the portal (which happened kind of gradually over the past year), that "Pinned" section was replaced with "Favorites". OK...not that big a deal...it's the same idea, and anything that was Pinned previously was now a Favorite. It only becomes confusing when you go into an Office app and still see the "Pinned" term. I mean, it's not THAT confusing, but it'd still be better if the same term were used.
Flash forward to about a month ago. I was giving my monthly SharePoint training and talking about the "Saved for later" thing. You know...in the "News from sites" section, you see a news post you want to read but don't have time, you click the little bookmark icon to "Save [it] for later". Only now, that "Saved for later" section in the sidebar on the SharePoint start page ALSO shows the (SharePoint-stored) files that I had "Pinned" or made a "Favorite".
So, at this point, we have three different terms being used for objects that a user wants to keep easily accessible. However, not all of those objects used to be in the same bucket. Now they are. Personally, I used those things differently because, having different names, I assumed they would remain separate. I like the "Save for later" concept for SharePoint pages/posts because I think it makes sense with how a lot of people use SharePoint. I also like "Pinned" and "Favorite" (although a common term would be fantastic) for marking files, Forms, Lists, etc. However, I don't like the combination of all these. It's just confusing to people. Maybe this is a transitional thing and there will be a single identifier used at some point later, but right now, it's really just causing frustration for our users.