Release Candidate (RC) is the build released internally to check if any critical problems have gone undetected into the code during the previous development period. Release candidates are NOT for production deployment, but they are for testing purposes only. However, in most of the cases, there are no differences between the final build and the last release candidate.
Release candidate and Beta testing are different. A release candidate has very few issues when compared to the Beta testing build.
If defects are found, then a round of testing is performed to ensure there are further issues.
Verify Installation issues for one final time.
Perform other critical workflow test against release candidate.