The no follow link is used for when you point a link to a site external to your web site. It comes into play when you are being provided compensation from the other website. As an example, say you have a link to Amazon as an affiliate seller on your website then you need to use no follow. Google does not like these types of follow links and has threaten to drop ranking on sites if they do not use no follow links.

If you are a sales representative then any links to companies your represent could be interrupted as needing no follow links.

I have been asking for this for a few years.

Ray