What is the meaning of erb?

erb stands for "Embedded RuBy". A .html.erb or .erb.html file is HTML with Ruby code embedded in; Rails will evaluate the Ruby to add content to the file dynamically, and will output a "pure" HTML file for rendering.

As @Chowlett mentioned before, erb stands for Embedded Ruby. When you define any file as ".html.erb" that means it's an HTML file with ruby code embedded in it and it is similar to ".rhtml" extension of rails file.

You can see a detailed and nice difference between ".html.erb" and ".rhtml" Click Here

Same as ".rhtml", you can also rename ".rjs" extension to ".js.erb" or ".rxml" to ".xml.erb"

This format separates out content type from template engine which is "erb" in this case.