Confidentiality
The CIA/ AIC triad i.e. Confidentiality, Integrity and Availability are a model specifically designed for guidance to an organization’s information security.
Confidentiality means unauthorized party/ individual cannot gain access to an organization’s sensitive data. If at all someone manages to gain access through unintentional behaviour then such a failure of confidentiality is called a breach.
For example, what if, your bank records are revealed on a public website that would be a breach.
In short, if anybody gains access to data/ information he/ she shouldn’t have an access to, then that is the confidentiality breach.