What is true friendship?

I’ve been thinking lately about what it means for someone to be a true friend, and I’d like to know what the Fluther community thinks. This is a pretty broad question, so I’m not looking for specifics, but I would like serious responses.

• Would you consider someone a true friend if you are on good terms (or “friends”) with them at work/school/etc, but never do anything with them outside of those circumstances?
• Can you really be a friend to someone without spending quality time with them?

Feel free to answer these specifically and/or the question in general.