One thing I dislike about Rails is its documentation.
I was watching this screencast http://railscasts.com/episodes/210-customizing-devise (at -7:00) and wanted to find out more about the before_filter.

Taken from http://api.rubyonrails.org/classes/A...-before_filter
before_filter(names, block)
Append a before filter. See #_insert_callbacks for parameter details.

Source: show | on GitHub
This doesn't really tell me much information.
Neither does #_insert_callbacks.
And the syntax seems different. There are no examples too.

How do I find out more about stuffs that I come across that I'm not sure of?
Are there better documentation with examples?

Can anyone tell me what type is the before_filter called, a controller method?
How to use it, and what other possible methods (if thats what its called) there are?