Referential, related to the word "reference," is a term that varies somewhat in meaning depending on the context of use. Basically though it refers to two or more objects, thoughts, sensory perception, emotional states, ideas, etc. that are linked to one another and require each other's presence to create meaning. In psychology, the idea of "self-reference" allows a client to build frames of reference that will help them to better identify emotional states and create a greater self-awareness.
For instance, an adult that was physically and verbally abused as a child will grow up internalizing the messages that they heard growing up as well as not understanding the boundary between appropriate discipline and abuse. Through analysis of the past this person can find "referentials" or points of reference that create reactions. This can lead a person to recognize how the words or actions of others trigger negative feelings about themself and then once recognized, use these methods (such as positive self-talk) to counter those bad feelings.