On typical Unix and Linux systems, programs would be able to pass a value to their parent processes while terminating. Values like these are referred to as Exit codes
As part of Snyk output you must have seen Snyk process terminating with exit codes, we typically see
Exit code 0 This means Snyk did not find vulnerabilities in your code an exited the process without failing the job. Exit code 1 This means Snyk found vulnerabilities in your code and have failed the build
You can read more about exit codes here