Following is the definition of the renamed, which I should have included previously:
Quick Scan --> Threat Scan
Threat Scan is the primary scan to choose because in almost all cases it catches all malware that a "Full Scan" would in less time. It scans for threats in all of the locations that malware likes to hide on your system, and ignoring places that it doesn't.
Flash Scan --> Hyper Scan
This was renamed because with the word "flash", it can be implied that this scan will search flash memory devices such as flash drives/thumbsticks, which it does not. This type of scan primarily searches for malicious processes that are currently running in memory. Because it takes less time to perform than a Threat Scan, it was renamed "Hyper Scan" to avoid the confusion with "flash".
Full Scan --> Custom Scan
A custom scan can be used to perform a full scan, that is, scanning every file and folder on every drive connected to the system. However, that's not its only function. A few specific directories can be selected as well instead of simply scanning everything.