Self-disclosure refers to a type of communication in which information about yourself is revealed. In terms of the Johari window, it is like taking information from the hidden self and moving it to the open self.  Usually self-disclosure is a conscious revealing of information, though it can sometimes occur with a slip of the tongue or unconscious verbal movements.  It is often reserved for intimate relationships as it is information that is previously unknown by the receiver (DeVito, 2005).

Factors Influencing Self-Disclosure

Identity: Highly sociably and extroverted people are more likely to self-disclose than those who exhibit shyness.  Also competent people reveal information more readily because they have great self-confidence and more positive things to reveal.
Culture: Different cultures view self-disclosure differently.  Research proves that Americans are more likely to self-disclose in certain situations than people of other nationalities. 
Gender: Research shows that women tend to self-disclose more than men, especially in terms of past relationships, friendships, greatest fears, etc.  The depth of disclosures also increases as the relationship grows more intimate.
Listeners: Dyads are the most hospitable structures for self-disclosure as you can attend to the responses carefully and monitor the disclosures.  It is also more likely for people to disclose information to people they like and know well.
Topic and Channel: There are some topics that prove more likely for self-disclosure than others.  For example, information about a job or interests are more likely to be disclosed than information about sexuality.  Also, the channel plays a role as research has shown that self-disclosure occurs more rapidly online than in face-to-face interactions.

(DeVito, 2005)