How is visualizing a text similar to or different from watching television or movies? For example, how is reading and visualizing Harry Potter and the Sorcerer's Stone different from watching the movie version?

Most of the time movies and television tend to change parts of a story. it can be little things and big things or major things. If you want to truly understand a story id suggest just reading the story. plus its important if you have to take a test or a quiz on it. trust me I had to learn the hard way, you wont pass a test on a book by watching the movie. Certain parts of the story can be changed or removed all together.