I’ve come to believe there are three different meanings of the term “Scrum” - well, three inside the software development community at least, if we consider sport we can probably add a fourth.
Even if nobody else does I differentiate between:
Scrum as a synonym of Agile
“Scrum” means “Agile” like “Hoover” means “Vaccum Cleaner” in English English, or like “QTips” means “Cotton Bugs” in American English, or increasingly “Google” means “Internet Search” whether you are using Google, Bing, Yahoo or some other search engine.
This is the way I believe a lot of software people use the term Scrum. Although Agile is more than Scrum alone often (mostly?) when people say Scrum they mean some a general form of Agile, something with iterations, stand-up meetings, perhaps User Stories, perhaps some technical practices, etc. etc.
Hard Core Scrum, ScrumTM
This is Scrum without Project Manager or Architects, maybe even without Testers. This is Scrum of Commitment and Abnormal Termination of Sprints.
I once heard Craig Larman say “If you have a project manager on a Scrum team you aren’t doing Scrum.” Only last week Christin Gorman Tweeted saying: “If you want to use managers and architects, you won't be doing scrum. And that's ok.”
I’ve written before about how this hard-core Scrum might actually conflict with Scrum (When did Scrum start loving Project Managers) and XP (Two ways to fill an iteration).
This view sees Scrum as a kind of Communist Manifesto but with Managers as the Bourgeoisie. It would be funny if this weren’t so serious. I believe that if you take this interpretation you will soon run into opposition from a layer of managers. The paradox is that Scrum is as popular as it is because those manager don’t like Extreme Programming and saw Scrum as the management friendly alternative (The Three Advantages of Scrum).
Common-Scrum or Scrum-Lite
This is Scrum but without the anti-manager zeal. Of course for many people this strips Scrum of its primary asset - and they might be right. It might be that if you neuter Scrum you get a less effective result.
In this form of Scrum Project Managers still exist - assuming you had them to start with, a lot of places don’t. However they have been renamed Scrum Masters - see my example from 2008.
In Scrum-lite the word commitment really means “agreement” because the team are probably using velocity to judge how much work they can do. Architects and other ranks, sorry, roles, still exists. And companies still kill teams - corporate psychiatry is rampant.
In other words: it is full of compromises. It works for some companies, it doesn’t work for others and ScrumTM purists will hate it.
Anyway, I find it useful to distinguish between these three uses of the term “Scrum”. If you know any more please add them to the list.