What is a requirement? Well, what kind?

From discussion on linkedin

"What are requirements"

https://www.linkedin.com/grp/post/128312-6019368539587121153

My comment:

A lot of comments already, have not read all of them, but i think the question is too wide. We need some adjectives in front of "requirement". I don't necessarily like all of them myself, but I offer up the ones I hear most: business, process, functional, non-functional , solution, system, even testing. 
I think what most comments here are speaking to is the functional requirement. While precise wording can vary, I hold that the definition must emphasize the concept of "what, not how". I like Jose Santos version, but would shorten it to "A software requirement describes what a software should do but not how to do it, and it satisfies a need." I also like where commentators use the term "future". Certainly a requirement stated now implies a future state where it is met, but it is good to state/think it instead of assuming the implication.

David Wright

prototyping tools are not new, and may already be hanging on your wall.

linkedin conversation on prototyping

https://www.linkedin.com/grp/post/60878-6021176829337944068

So, key man theory and agile.

Later than I thought, but have always wondered about the Product Manager in the agile approaches that feature the role. They are the go-to person for the rest of the team with questions about what is being delivered, yes? What if that person, for any reason, has to leave the project before it completes? What impact does that have? Or am
I asking a rhetorical question?