When you start learning programming in Ruby you’ll need three tools: A text editor, a terminal, and a Ruby runtime.
As a programmer you’ll spend tons of time working with your text editor and terminal (or “in” them, as we say). It makes sense for you to learn how to use these tools, and how to customize them so they fit your taste.
There are also text editors that can be integrated into a terminal window. This means you don’t have to switch between applications. There are also online services that integrate all of this as a web application, with a nice interface in your browser.
Feel free to try all these things out, and play with them as much as you like. However, for our study groups, we have found that using the simplest tools possible, at least for a while, works best: It reduces the amount of things people need to learn in the beginning, and everyone learns the same few basic things that are required to run a Ruby program in this environment.