If you get an email or see a message in the Notifications section of your dashboard saying that you have a Reference Request, it means someone that you are colleagues with wants you to write a professional reference for them.
BiggerPockets gives our members the ability to request references from others on the site that they are connected to, in order to help establish trust. If you get a request from someone that you don't know very well, or who you haven't done business with, we recommend you Deny the request instead of writing nothing of substance.
If, however, you do know the person well, and have worked with them, a well-written reference explains your relationship, and tells others how the person was to work with.
All of your references will appear on your Profile.