I have questions on modifying an extension (Huot's File more specifically)

Greetings all, second time poster, long time listener.

So I’ve been trying to modify Mark Huots “file” extension in order to add other form fields attached to specific images uploaded. I’ve been reading diligently through the EE Documentation and Developer area and I’m afraid I can’t find my answer or at least don’t understand it.

My main question is about hooks. There is no real great explanation about hooks and how they work in the EE Docs, and I understand that I need to understand them 😊.

Here are the questions: What is the philosophy and the magic behind hooks? How do I generate form fields?

In the case of Mark huot’s file, I can see that there is a table created, and I understand how, in the extension, to add the fields I want to track.

Here are my modification requirements: I wish to add an alt, title and description field for images that aren’t thumbnails. I wish to add a title and description field for flash movies, as well as the proper html involved. I want to add templates tags for the above.

No small feet indeed, but something is not clicking in how to create the custom form fields properly, attach them to the file extension and then add them to the templates.

Any help would be greatly appreciated and rewarded with messages of heaping praise.

Thanks, Kenny