Confidentiality, Integrity, and Availability are known as the CIA triad.

Confidentiality

Confidentiality is how we keep sensitive data secure and private, and only share that data with its intended audience. Confidentiality is equivalent to privacy.

We can ensure data is kept confidential by encrypting our data both at rest and in transit. Credentials should be stored correctly and multi-factor authentication should be implemented.

Integrity

Integrity means ensuring the consistency, accuracy, and trustworthiness of data across its entire life-cycle. This means we don't want unauthorized people to be able to change data in transit or when in storage, which would also breach confidentiality.

Things to consider for maintaining integrity is ensuring the correct file permissions are in place, user access control is implemented properly, and version control is in place - to ensure there are no erroneous changes or deletions of data.

You can ensure data or software is integral with the use of check-sums, which is a verified hash that can be checked by the user.

Availability

Availability is all about ensuring systems are available, with effective redundancy implemented across everything. You should also design your architectures with failure in mind.

A related model is the AAA Model, which is used to compliment the CIA triad; the acronym is composed of Authentication, Authorization, and Accounting.