An RB file is an object-oriented scripting language software program written in Ruby. Being written in Ruby makes it easy to read, simple and efficient. You can edit RB files using a text editor and run them through Ruby. There are different versions of Ruby available. You can also refer to them as gems, and typical examples include Ruby on Rails, Capistrano, and Mongrel. It would help to note that automated repetitive tasks on Google Sketchup 4 use Ruby files. Older versions of Real Studio also used RB files, but the newer versions use a different extension, .RBP.