I encourage you to review “Who This Book Is For” on page xv. The book presumes that you are a programmer who understands at least how to read HTML. Just not necessarily a programmer who has experience with the Ruby language.

If you don’t already know what a method is (from other languages, perhaps), you likely won’t have made it past the term “object oriented” earlier in this chapter.

As to irb: that is mentioned much later in the book. Meanwhile the purpose of this chapter is to introduce you to just enough of the Ruby language to get onto the real purpose of the book: learning Rails.

Does this make sense?