Tutorial for Category Menus

I might be a little slow on this feature, but I'm having a hard time understanding it.

I understand the ability to create an indented menu structure, but what's the "content" field for? Can I use this for an entire site structure, kinda like I use Multi Record sections for single level menus?

Is there a tutorial on this capability? I didn't see one in the docs, but may have overlooked it?

I've read some posts that talk about getCategories instead of getRecords, but don't know where to find the docs that show what getCategories returns vs what getRecords returns...and for that matter, why would I use it and not getRecords?

Any info would be great - I just need a nudge in the right direction on this one.

Thanks,
Gary