Topic: REST & Controller Actions

I'm working on an old Rails 2.3.14 application.
I'm familiar with controller actions that look like...

def update
  # ... code ...
end

But in this application I'm seeing actions that look like...

update
  # ... code ...
end

I'm confused as to why the def is no longer needed.
To make matters even worse below that is this action...

update.before
  # ... code ...
end

Can someone please enlighten me? 
I tried Google, but didn't have much luck.