In Ruby Essential Training, expert instructor Kevin Skoglund teaches the fundamentals of Ruby, the popular object-oriented open-source programming language. Kevin begins by walking through the basic data types, demonstrating Ruby's control structures (loops, iterators, conditionals, and code blocks) and showcasing the elegant syntax structure of the language. Kevin explains variable scope and shows how to use methods, arguments, and return values to write efficient code. After covering the fundamentals, Kevin focuses on Ruby's object-oriented features. He shows how to define classes and explores OOP concepts, including instances, attributes, access control, and inheritance. Exercise files accompany the course.