In cybersecurity three main goals are specified:
If something is classified as confidential no unauthorized person should be able to read your data. This is meant by the term confidentiality.
The goal of integrity means nobody is able to change your data. It could happen that someone is able to read your data. Then the goal of confidentiality is affected. But if the person is not able to change your data integrity is ensured.
May it be a hardware failure, a software malfunction or a malicious cyber attack - there are situations a customer can’t reach your resource or system. This is called the downtime. Availability is the goal to minimize the downtime.