Confidentiality, integrity, and availability comprise the CIA triad, a model used to guide the areas of focus for computer security. These three foundational objectives drive the development of policies, form the basis for information security plans, and are the principles for developing benchmarks to assess security.
Confidentiality ensures that only authorized users have access to data. Integrity means assuring that data remains in its intended state and is only edited by authorized personnel. Availability is defined as providing the right access to systems and data when and where needed. Together, the CIA triad provides a solid baseline for computer security.
There are two additional objectives that are often included in security evaluations and plans: authentication and nonrepudiation. Authentication is the process by which credentials are presented and validated to enable access. Nonrepudiation ensures authenticity such that the originator cannot deny identity.
For longer definitions, read:
The impact of breaches of any of the five is discussed in FIPS PUB 199 Standards for Security Categorization of Federal Information and Information Systems on pages 2–6.