Perform variety of operations on a rich text document.

This post is among my first few steps towards learning Ruby. For learning it fast, I want to make a real application and apply the concepts with what I am learning using a book. I am making a text editor wherein a user can perform variety of operations and can even convert it to a rich text.

Here are my first set of queries:

(1) I want to provide the user a screen wherein they can type-in text. How to do this? Which control and what-so-ever is involved?

(2) When the user has entered text, how to perform operations on the text. Do I need to take it in a buffer or something better? A user can select a portion of text and my program must determine that portion and perform operations on it.